Use of inhibitors of glutaminyl cyclases for treatment and prevention of disease

ABSTRACT

The present invention provides novel physiological substrates of mammalian glutaminyl cyclase (QC, EC 2.3.2.5), new effectors of QC, methods for screeing for such effectors, and the use of such effectors and pharmaceutical compositions comprising such effectors for the treatment of conditions that can be treated by modulation of QC-activity. Preferred compositions additionally comprise inhibitors of DP IV or DP IV-like enzymes for the treatment or alleviation of conditions that can be treated by modulation of QC- and DP IV-activity.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit from U.S. provisional application Ser.Nos. 60/468,043 filed on May 5, 2003, 60/512,038 filed on Oct. 15, 2003,and 60/468,014 filed on May 5, 2003, which are incorporated herein byreference in their entirety.

FIELD OF THE INVENTION

The invention relates to glutaminyl cyclase (QC, EC 2.3.2.5) thatcatalyzes the intramolecular cyclization of N-terminal glutamineresidues into pyroglutamic acid (5-oxo-proline, pGlu*) under liberationof ammonia and the intramolecular cyclization of N-terminal glutamateresidues into pyroglutamic acid under liberation of water.

The present invention identifies mammalian QCs as metalloenzymes,provides novel physiological substrates of QC in mammals and the use ofeffectors of QC and pharmaceutical compositions comprising effectors ofQC for the treatment of conditions that can be treated by modulation ofQC-activity. Additionally, it is shown that metal interaction is auseful approach for development of QC inhibitors.

In a preferred embodiment, the present invention provides the use ofeffectors of QC activity in combination with inhibitors of DP IV or DPIV-like enzymes for the treatment or alleviation of conditions that canbe treated by modulation of QC- and/or DP IV-activity.

A screening method is also provided for the identification and selectionof effectors of QC activity.

BACKGROUND

Glutaminyl cyclase (QC, EC 2.3.2.5) catalyzes the intramolecularcyclization of N-terminal glutamine residues into pyroglutamic acid(pGlu*) liberating ammonia. A QC was first isolated by Messer from thelatex of the tropical plant Carica papaya in 1963 (Messer, M. 1963Nature 4874, 1299). 24 years later, a corresponding enzymatic activitywas discovered in animal pituitary (Busby, W. H. J. et al. 1987 J BiolChem 262, 8532-8536; Fischer, W. H. and Spiess, J. 1987 Proc Natl AcadSci USA 84, 3628-3632). For the mammalian QC, the conversion of Gln intopGlu by QC could be shown for the precursors of TRH and GnRH (Busby, W.H. J. et al. 1987 J Biol Chem 262, 8532-8536; Fischer, W. H. and Spiess,J. 1987 Proc Natl Acad Sci USA 84, 3628-3632). In addition, initiallocalization experiments of QC revealed a co-localization with itsputative products of catalysis in bovine pituitary, further improvingthe suggested function in peptide hormone synthesis (Bockers, T. M. etal. 1995 J Neuroendocrinol 7, 445-453). In contrast, the physiologicalfunction of the plant QC is less clear. In case of the enzyme from C.papaya, a role in the plant defense against pathogenic microorganismswas suggested (El Moussaoui, A. et al. 2001 Cell Mol Life Sci 58,556-570). Putative QCs from other plants were identified by sequencecomparisons recently (Dahl, S. W. et al.2000 Protein Expr Purif 20,27-36) The physiological function of these enzymes, however, is stillambiguous.

The QCs known from plants and animals show a strict specificity forL-Glutamine in the N-terminal position of the substrates and theirkinetic behavior was found to obey the Michaelis-Menten equation (Pohl,T. et al. 1991 Proc Natl Acad Sci USA 88, 10059-10063; Consalvo, A. P.et al. 1988 Anal Biochem 175, 131-138; Gololobov, M. Y. et al. 1996 BiolChem Hoppe Seyler 377, 395-398). A comparison of the primary structuresof the QCs from C. papaya and that of the highly conserved QC frommammals, however, did not reveal any sequence homology (Dahl, S. W. etal. 2000 Protein Expr Purif 20, 27-36). Whereas the plant QCs appear tobelong to a new enzyme family (Dahl, S. W. et al. 2000 Protein ExprPurif 20, 27-36), the mammalian QCs were found to have a pronouncedsequence homology to bacterial aminopeptidases (Bateman, R. C. et al.2001 Biochemistry 40, 11246-11250), leading to the conclusion that theQCs from plants and animals have different evolutionary origins.

EP 02 011 349.4 discloses polynucleotides encoding insect glutaminylcyclase, as well as polypeptides encoded thereby. This applicationfurther provides host cells comprising expression vectors comprisingpolynucleotides of the invention. Isolated polypeptides and host cellscomprising insect QC are useful in methods of screening for agents thatreduce glutaminyl cyclase activity. Such agents are described as usefulas pesticides.

Alzheimer's disease (AD) is characterized by abnormal accumulation ofextracellular amyloidotic plaques closely associated with dystrophicneurones, reactive astrocytes and microglia (Terry, R. D. and Katzman,R. 1983 Ann Neurol 14, 497-506; Glenner, G. G. and Wong, C. W. 1984Biochem Biophys Res Comm 120, 885-890; Intagaki, S. et al. 1989 JNeuroimmunol 24, 173-182; Funato, H. et al. 1998 Am J Pathol 152,983-992; Selkoe, D. J. 2001 Physiol Rev 81, 741-766). Amyloid-β (Aβ)peptides are the primary components of senile plaques and are consideredto be directly involved in the pathogenesis and progression of AD, ahypothesis supported by genetic studies (Glenner, G. G. and Wong, C. W.1984 Biochem Biophys Res Comm 120, 885-890; Borchelt, D. R. et al. 1996Neuron 17, 1005-1013; Lemere, C. A. et al. 1996 Nat Med 2, 1146-1150;Mann, D. M. and Iwatsubo, T. 1996 Neurodegeneration 5, 115-120; Citron,M. et al. 1997 Nat Med 3, 67-72; Selkoe, D. J. 2001 Physiol Rev 81,741-766). Aβ is generated by proteolytic processing of the β-amyloidprecursor protein (APP) (Kang, J. et al. 1987 Nature 325, 733-736;Selkoe, D. J. 1998 Trends Cell Biol 8, 447-453), which is sequentiallycleaved by β-secretase at the N-terminus and by γ-secretase at theC-terminus of Aβ (Haass, C. and Selkoe, D. J. 1993 Cell 75, 1039-1042;Simons, M. et al. 1996 J Neurosci 16 899-908). In addition to thedominant Aβ peptides starting with L-Asp at the N-terminus (Aβ1-42/40),a great heterogeneity of N-terminally truncated forms occurs in senileplaques. Such shortened peptides are reported to be more neurotoxic invitro and to aggregate more rapidly than the full-length isoforms (Pike,C. J. et al. 1995 J Biol Chem 270 23895-23898). N-truncated peptides areknown to be overproduced in early onset familial AD (FAD) subjects(Saido, T. C. et al. 1995 Neuron 14, 457-466; Russo, C. et al. 2000Nature 405, 531-532), to appear early and to increase with age in Down'ssyndrome (DS) brains (Russo, C. et al. 1997 FEBS Lett 409, 411-416,Russo, C. et al. 2001 Neurobiol Dis 8, 173-180; Tekirian, T. L. et al.1998 J Neuropathol Exp Neurol 57, 76-94). Finally, their amount reflectsthe progressive severity of the disease (Russo, C. et al. 1997 FEBS Lett409, 411-416). Additional post-translational processes may furthermodify the N-terminus by isomerization or racemization of the aspartateat position 1 and 7 and by cyclization of glutamate at residues 3 and11. Pyroglutamate-containing isoforms at position 3 [pGlu³]Aβ3-40/42]represent the prominent forms—approximately 50% of the total Aβamount—of the N-truncated species in senile plaques (Mori, H. et al.1992 J Biol Chem 267, 17082-17086, Saido, T. C. et al. 1995 Neuron 14,457-466; Russo, C. et al. 1997 FEBS Lett 409, 411-416; Tekirian, T. L.et al. 1998 J Neuropathol Exp Neurol 57, 76-94; Geddes, J. W. et al.1999 Neurobiol Aging 20, 75-79; Harigaya, Y. et al. 2000 Biochem BiophysRes Commun 276, 422-427) and they are also present in pre-amyloidlesions (Lalowski, M. et al. 1996 J Biol Chem 271, 33623-33631). Theaccumulation of AβN3(pE) peptides is likely due to the structuralmodification that enhances aggregation and confers resistance to mostamino-peptidases (Saido, T. C. et al. 1995 Neuron 14, 457-466; Tekirian,T. L. et al. 1999 J Neurochem 73, 1584-1589).

This evidence provides clues for a pivotal role of AβN3(pE) peptides inAD pathogenesis. However, relatively little is known about theirneurotoxicity and aggregation properties (He, W. and Barrow, C. J. 1999Biochemistry 38, 10871-10877; Tekirian, T. L. et al. 1999 J Neurochem73, 1584-1589). Moreover, the action of these isoforms on glial cellsand the glial response to these peptides are completely unknown,although activated glia is strictly associated to senile plaques andmight actively contribute to the accumulation of amyloid deposits. Inrecent studies the toxicity, aggregation properties and catabolism ofAβ1- 42, Aβ1-40, [pGlu³]Aβ3-42 and [pGlu³]Aβ3-40 peptides wereinvestigated in neuronal and glial cell cultures, and it was shown thatpyroglutamate modification exacerbates the toxic properties ofAβ-peptides and also inhibits their degradation by cultured astrocytes.Shirotani et al. investigated the generation of [pGlu³]Aβ peptides inprimary cortical neurons infected by Sindbis virus in vitro. Theyconstructed amyloid precursor protein complementary DNAs, which encodeda potential precursor for [pGlu³]Aβ by amino acid substitution anddeletion. For one artificial precursor starting with a N-terminalglutamine residue instead of glutamate in the natural precursor, aspontaneous conversion or an enzymatic conversion by glutaminyl cyclaseto pyroglutamate was suggested. The cyclization mechanism of N-terminalglutamate at position 3 in the natural precursor of [pGlu ³]Aβ was notdetermined in vivo (Shirotani, K., Tsubuki, S., Lee, H. J., Maruyama,K., and Saido, T. C. (2002) Neurosci Lett 327, 25-28)

Dipeptidyl peptidase IV (DP IV) is a post-proline (to a lesser extentpost-alanine, post-serine or post-glycine) cleaving serine proteasefound in various tissues of the body including kidney, liver, andintestine and cleaves N-terminal dipeptides from a peptide chain.Recently it was shown that DP IV plays an important role in neuropeptidemetabolism, T-cell activation, attachment of cancer cells to theendothelium and the entry of HIV into lymphoid cells. See therefore WO02/34242, WO 02/34243, WO 03/002595 and WO 03/002596.

It is known that DP IV inhibitors may be useful for the treatment ofimpaired glucose tolerance and diabetes mellitus (International PatentApplication, Publication Number WO 99/61431, Pederson, R. A. et al. 1998Diabetes 47, 1253-1258 and Pauly, R. P. et al. 1999 Metabolism 48,385-389). In particular WO 99/61431 discloses DP IV inhibitorscomprising an amino acid residue and a thiazolidine or pyrrolidinegroup, and salts thereof, especially L-threo-isoleucyl thiazolidine,L-allo-isoleucyl thiazolidine, L-threo-isoleucyl pyrrolidine,L-allo-isoleucyl thiazolidine, L-allo-isoleucyl pyrrolidine, and saltsthereof.

Further examples of low molecular weight dipeptidyl peptidase IVinhibitors are agents such as tetrahydroisoquinolin-3-carboxamidederivatives, N-substituted 2-cyanopyroles and -pyrrolidines,N-(N′-substituted glycyl)-2-cyanopyrrolidines, N-(substitutedglycyl)-thiazolidines, N-(substituted glycyl)-4-cyanothiazolidines,amino-acyl-borono-prolyl-inhibitors, cyclopropyl-fused pyrrolidines andheterocyclic compounds. Inhibitors of dipeptidyl peptidase IV aredescribed in U.S. Pat. No. 6,380,398, U.S. Pat. No. 6,011,155; U.S. Pat.No. 6,107,317; U.S. Pat. No. 6,110,949; U.S. Pat. No. 6,172,081; WO95/15309, WO 99/61431, WO 99/67278, WO 99/67279, DE 198 34 591, WO97/40832, DE 196 16 486 C 2, WO 98/19998, WO 00/07617, WO 99/38501, WO99/46272, WO 99/38501, WO 01/68603, WO 01/40180, WO 01/81337, WO01/81304, WO 01/55105, WO 02/02560 and WO 02/14271, WO 02/04610, WO02/051836, WO 02/068420, WO 02/076450; WO 02/083128, WO 02/38541, WO03/000180, WO 03/000181, WO 03/000250, WO 03/002530, WO 03/002531, WO03/002553, WO 03/002593, WO 03/004496, WO 03/024942 and WO 03/024965,the teachings of which are herein incorporated by reference in theirentirety, especially concerning these inhibitors, their definition, usesand their production.

SUMMARY OF THE INVENTION

The present invention provides novel physiological substrates of QC inmammals, Aβ3-40/42, [Gln³]Aβ3-40/42, [Glu¹¹]Aβ11-40/42,[Gln¹¹]Aβ11-40/42, [Gln¹]Gastrin, [Gln¹]Neurotensin, [Gln¹]FPP,[Gln¹]CCL 2, [Gln¹]CCL 7, [Gln¹]CCL 8, [Gln¹]CCL 16, [Gln¹]CCL 18,[Gln¹]Fractalkine, [Gln¹]Orexin A, [Gln³]glucagon3-29 and[Gln⁵]substance P5-11 and the use of effectors of QC and pharmaceuticalcompositions comprising effectors of QC for the treatment of conditionsthat can be treated by modulation of QC activity.

It was shown by inhibition studies that human QC is a metal-dependenttransferase. QC apoenzyme could be reactivated most efficiently by zincions, and the metal-binding motif of zinc-dependent aminopeptidases isalso present in human QC. Compounds interacting with the active-sitebound metal are potent inhibitors.

Unexpectedly, it was shown that recombinant human QC as well asQC-activity from brain extracts catalyze both, the N-terminal glutaminylas well as glutamate cyclization. Most striking is the finding, thatcyclase-catalyzed Glu¹-conversion is favored around pH 6.0 whileGln¹-conversion to pGlu-derivatives occurs with a pH-optimum of around8.0. Since the formation of pGlu-Aβ-related peptides can be suppressedby inhibition of recombinant human QC and QC-activity from pig pituitaryextracts, the enzyme QC is a target in drug development for treatment ofAlzheimer's disease.

By administering effectors of QC activity to a mammal it can be possibleto prevent or alleviate or treat conditions selected from Alzheimer'sdisease, Down Syndrome, ulcer disease and gastric cancer with or w/oHeliobacter pylori infections, pathogenic psychotic conditions,schizophrenia, infertility, neoplasia, inflammatory host responses,cancer, psoriasis, rheumatoid arthritis, atherosclerosis, impairedhumoral and cell-mediated immune responses, leukocyte adhesion andmigration processes in the endothelium, impaired food intake,sleep-wakefulness, impaired homeostatic regulation of energy metabolism,impaired autonomic function, impaired hormonal balance and impairedregulation of body fluids.

Further, by administration of effectors of QC activity to a mammal itcan be possible to stimulate gastrointestinal tract cell proliferation,preferably proliferation of gastric mucosal cells, epithelial cells,acute acid secretion and the differentiation of acid producing parietalcells and histamine-secreting enterochromaffin-like cells.

Furthermore, by administration of effectors of QC activity to a mammalit can be possible to suppress the proliferation of myeloid progenitorcells.

In addition, administration of QC inhibitors can lead to suppression ofmale fertility.

In a preferred embodiment, the present invention provides the use ofeffectors of QC activity in combination with inhibitors of DP IV or DPIV-like enzymes for the treatment or alleviation of conditions that canbe treated by modulation of QC- and/or DP IV-activity.

The present invention provides pharmaceutical compositions forparenteral, enteral or oral administration, comprising at least oneeffector of QC optionally in combination with customary carriers and/orexcipients; or comprising at least one effector of QC in combinationwith at least one DP IV-inhibitor, optionally in combination withcustomary carriers and/or excipients.

Screening methods are also provided for the identification and selectionof effectors of QC.

BRIEF DESCRIPTION OF THE DRAWINGS

Further understanding of these and other aspects of the presentinvention will be had by reference to the figures wherein:

FIG. 1 shows progress curves of the cyclization of H-Gln-Ala-OH,catalyzed by human QC, monitoring the decrease in absorbance at 340 nm.The samples contained 0.3 mM NADH/H⁺, 14 mM α-Ketoglutaric acid, 30 U/mlglutamic dehydrogenase and 1 mM H-Gln-Ala-OH. From curve A-D, varyingconcentrations of QC were applied: A, 10 mU/ml, B, 5 mU/ml, C, 2.5mU/ml. In case of curve D, QC was omitted. A linear relationship wasobtained between the QC concentration and the observed activity (inset).

FIG. 2 shows the pH dependence of human and papaya (inset) QC,determined under first-order rate conditions using Gln-βNA as substrate.In case of human QC, a buffer system providing a constant ionic strengthaccording to Ellis and Morrison was used, consisting of 25 mM MES, 25 mMacetic acid and 50 mM Tris (Ellis, K. J. and Morrison, J. F. 1982Methods Enzymol. 87, 405-426). Due to a slightly inhibiting effect ofTris, papaya QC was investigated using a 50 mM Mops buffer. The ionicstrength was adjusted to 0.05 M by addition of NaCl. The rate profileswere evaluated by fitting to a model that is based on dissociatinggroups. In case of papaya QC, a pK_(a) of 7.13±0.03 was obtained byfitting of the data to a single dissociation model.

FIG. 3 shows the effect of the pH on the stability of the QC from Papayalatex and human QC. An enzyme stock solution was diluted 20-fold in 0.1M buffer of various pH values (pH 4-7 sodium citrate, pH 7-10 sodiumphosphate). Enzyme solutions were incubated at 30° C. for 30 min andsubsequently enzymatic activity was analyzed according to the standardprotocol.

FIG. 4 shows the comparison of the specificity constant k_(cat)/K_(M)for a set of substrates containing glutamate in the second amino acidposition (peptides are disclosed as SEQ ID NOS 23, 24, 26, 22, and 25,respectively in order of appearance from left to right). Whereas anincrease in specificity of human QC was detected from the di- to thetetrapeptides, no change was observed in case of papaya QC. The datapresented here is a replot of the parameters given in Table 3.

FIG. 5 shows the formation of pGlu-Lys(pGlu)-Arg-Leu-Ala-NH₂ fromH-Gln-Lys(Gln)-Arg-Leu-Ala-NH₂, catalyzed by human QC. Substrateconversion is monitored by a time-dependent change in the m/z ratio dueto the expulsion of ammonia. The sample composition was 0.5 mMsubstrate, 38 nM QC in 40 mM Tris/HCl, pH 7.7. At the times indicated,samples were removed from the assay tube, mixed with matrix solution(1:1 v/v) and subsequently the mass spectra recorded. A very similardependence was observed in case of papaya QC.

FIG. 6 shows the formation of pGlu-Phe-Lys-Ala-Glu-NH₂ (SEQ ID NO: 1)from H-Gln(NMe)-Phe-Lys-Ala-Glu-NH₂ (SEQ ID NO: 2) catalyzed by papayaQC. Substrate conversion is monitored by a time-dependent change in them/z ratio due to the expulsion of methylamine. The sample compositionwas 0.5 mM substrate, 0.65 μM papaya QC in 40 mM Tris/HCl, pH 7.7. Atthe times indicated, samples were removed from the assay tube, mixedwith matrix solution (1:1 v/v) and subsequently the mass spectrarecorded. No substrate conversion was observed in samples without papayaQC or by applying up to 1.5 μM human QC to the substrate (not shown).

FIG. 7 shows the formation of [Gln³]-Aβ3-11 from [Gln³]Aβ1-11 catalysedby DPIV. At the times indicated, samples were removed, from the assaytube, mixed with matrix solution (1:1 v/v) and subsequently the massspectra recorded.

FIG. 8 shows the prevention of the cleavage of [Gln³]Aβ1-11 by the DPIV-inhibitorVal-Pyrrolidide (Val-Pyrr). At the times indicated, sampleswere removed from the assay tube, mixed with matrix solution (1:1 v/v)and subsequently the mass spectra recorded.

FIG. 9 shows the formation of [pGlu³]Aβ3-11 from [Gln³]Aβ3-11 catalyzedby QC. At the times indicated, samples were removed from the assay tube,mixed with matrix solution (1:1 v/v) and subsequently the mass spectrarecorded.

FIG. 10 shows the inhibition of the formation of [pGlu³]Aβ3-11 from[Gln³]Aβ3-11 by the QC-inhibitor 1,10-phenanthroline. At the timesindicated from the assay tube, samples were removed, mixed with matrixsolution (1:1 v/v) and subsequently the mass spectra recorded.

FIG. 11 shows the formation of [pGlu³]Aβ3-11 from [Gln³]Aβ1-11 afterconsecutive catalys by DP IV and QC. At the times indicated, sampleswere removed from the assay tube, mixed with matrix solution (1:1 v/v)and subsequently the mass spectra recorded.

FIG. 12 shows the inhibition of [pGlu³]Aβ3-11 formation from[Gln³]Aβ1-11 by the QC-inhibitor 1,10-phenanthroline in the presence ofcatalytically active DP IV and QC. At the times indicated, samples wereremoved from the assay tube, mixed with matrix solution (1:1 v/v) andsubsequently the mass spectra recorded.

FIG. 13 shows the reduction of [pGlu³]Aβ3-11 formation from [Gln³]Aβ1-11by the DP IV-inhibitor Val-Pyrr in the presence of catalytically activeDP IV and QC. At the times indicated, samples were removed from theassay mixture, mixed with matrix solution (1:1 v/v) and subsequently themass spectra recorded.

FIG. 14 shows the formation of [pGlu³]Aβ-peptide3-11 from [Gln³]Aβ1-11after consecutive catalysis by aminopeptidase(s) and QC that are presentin porcine pituitary homogenate. At the times indicated, samples wereremoved from the assay tube, mixed with matrix solution (1:1 v/v) andsubsequently the mass spectra recorded.

FIGS. 15A and B show Mass spectra of Aβ3-11a and Aβ3-21a incubated withrecombinant human QC, that was boiled for 10 min before use. C and Dshow Mass spectra of Aβ3-11 and Aβ3-21a in presence of active human QCresulting in the formation of [pGlu³]Aβ3-11a and [pGlu³]Aβ3-21a,respectively. E and F show Mass spectra of Aβ3-11a and Aβ3-21a inpresence of active QC and 5 mM Benzimidazole suppressing the formationof [pGlu³]formation.

FIG. 16 shows reaction rates of papaya QC- catalyzed Glu-βNA-conversionplotted against the substrate concentration. The initial rates weremeasured in 0.1 M pyrophosphate buffer, pH 6.1 (squares), 0.1 Mphosphate buffer, pH 7.5 (circles) and 0.1 M borate buffer, pH 8.5(triangles). The kinetic parameters were as follows: K_(M)=1.13±0.07 mM,k_(cat)=1.13±0.04 min⁻¹ (pH 6.1); K_(M)=1.45±0.03 mM, k_(cat)=0.92±0.01min⁻¹ (pH 7.5); K_(M)=1.76±0.06 mM, k_(cat)=0.56±0.01 min⁻¹ (pH 8.5).

FIG. 17 shows the pH-dependence of the conversion of Gln-βNA (circles)and Glu-βNA (squares), determined under first-order rate-law conditions(S<<K_(M)). Substrate concentration was 0.01 mM and 0.25 mM,respectively. For both determinations, a three-component buffer systemwas applied consisting of 0.05 M acetic acid, 0.05 M pyrophosphoric acidand 0.05 M Tricine. All buffers were adjusted to equal conductivity byaddition of NaCl, in order to avoid differences in ionic strength. Thedata were fitted to equations that account for two dissociating groupsrevealing pK_(a)-values of 6.91±0.02 and 9.5±0.1 for Gln-βNA and 4.6±0.1and 7.55±0.02 for Glu-βNA. The pK_(a)-values of the respective substrateamino groups, determined by titration, were 6.97±0.01 (Gln-βNA) and7.57±0.05 (Glu-βNA). All determinations were carried out at 30° C.

FIG. 18 shows progress curves of human QC-catalyzed cyclization ofH-Gln-AMC in presence of imidazole, dipicolinic acid and in absence ofan inhibitory compound. The hyperbolic shape of the curve in presence ofdipicolinic acid indicates metal ion remove from the active site of QC.

FIG. 19 shows the time-dependent inactivation of QC by the heterocyclicchelator 1,10-phenanthroline. After incubation of the QC-enzyme with theinhibitor in absence of substrate (continuous line), a reduced enzymaticactivity was observed compared to samples that were not preincubatedwith inhibitor (dotted trace), indicating metal ion remove from theactive site of QC.

FIG. 20 shows the reactivation of human QC with monovalent- and divalentmetal ions. QC was inactivated by addition of 2 mM dipicolinic acid in50 mM Bis-Tris, pH 6.8. Subsequently, the enzyme was subjected todialysis against 50 mM Bis-Tris, pH 6.8, containing 1.0 mM EDTA.Reactivation of the enzymes was achieved by incubation of theinactivated enzyme sample with metal ions at a concentration of 0.5 mM,in presence of 0.5 mM EDTA in order to avoid an unspecific reactivationby traces of metal ions present in buffer solutions. Controls are givenby enzyme samples that were not inactivated, but also dialyzed againstEDTA solution as the inactivated enzyme (+EDTA) and enzyme samples thatwere dialyzed against buffer solutions without added EDTA (−EDTA).

FIG. 21 Sequence alignment of human QC (hQC) and other M28 familymembers of the metallopeptidase Clan MH. Multiple sequence alignment wasperformed using ClustalW at ch.EMBnet.org with default settings. Theconservation of the zinc-ion ligating residues is shown for human QC(hQC; GenBank X71125), the Zn-dependent aminopeptidase from Streptomycesgriseus (SGAP; Swiss-Prot P80561), and within theN-acetylated-alpha-linked acidic dipeptidase (NAALADase I) domain(residues 274-587) of the human Glutamate carboxypeptidase II (hGCP II;Swiss-Prot Q04609). The amino acids involved in metal binding are typedin bold and underlined. In case of human QC, these residues are theputative counterparts to the peptidases.

PEPTIDE SEQUENCES

The peptides mentioned and used herein have the following sequences:

Aβ1-42: Asp-Ala-Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys-Leu-Val-Phe-Phe-Ala-Glu-Asp-Val-Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu-Met-Val- Gly-Gly-Val-Val-Ile-AlaAβ1-40: Asp-Ala-Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys-Leu-Val-Phe-Phe-Ala-Glu-Asp-Val-Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu-Met-Val- Gly-Gly-Val-Val Aβ3-42:Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys-Leu-Val-Phe-Phe-Ala-Glu-Asp-Val-Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu-Met-Val-Gly-Gly- Val-Val-Ile-Ala Aβ3-40:Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys-Leu-Val-Phe-Phe-Ala-Glu-Asp-Val-Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu-Met-Val-Gly-Gly- Val-Val Aβ1-11a:Asp-Ala-Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-NH₂ Aβ3-11a:Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-NH₂ Aβ1-21a:Asp-Ala-Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys-Leu-Val-Phe-Phe-Ala-NH₂ Aβ3-21a:Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys-Leu-Val-Phe-Phe-Ala-NH₂ Gln³-Aβ3-40:Gln-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys-Leu-Val-Phe-Phe-Ala-Glu-Asp-Val-Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu-Met-Val-Gly-Gly- Val-Val Gln³-Aβ3-21a:Gln-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys-Leu-Val-Phe-Phe-Ala-NH₂ Gln³-Aβ1-11a:Asp-Ala-Gln-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-NH₂ Gln³-Aβ3-11a:Gln-Phe-Arg-His-Asp-Ser-Gly-Tyr-Glu-NH₂

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides effectors of glutaminyl cyclase (QC) for

-   -   a) the treatment of diseases in mammals that can be treated by        modulation of QC activity in vivo and/or    -   b) the modulation of physiological processes based on the action        of pGlu-containing peptides caused by modulation of QC activity.

Furthermore, the present invention provides compounds for the inhibitionof glutaminyl cyclase (QC, EC 2.3.2.5) and/or QC-like enzymes in amammal and the use of inhibitors of QC activity for the treatment ofpathological conditions related to QC activity.

The present invention also provides a new method for the treatment ofAlzheimer's disease and Down Syndrome. The N-termini of amyloidβ-peptides deposited in Alzheimer's disease and Down syndrome brain bearpyroglutamic acid. The pGlu formation is an important event in thedevelopment and progression in the disease, since the modified amyloidβ-peptides show an enhanced tendency to β-amyloid aggregation andtoxicity, likely worsening the onset and progression of the disease.(Russo, C. et al. 2002 J Neurochem 82,1480-1489).

In contrast, in the natural Aβ-peptides (3-40/42), glutamic acid ispresent as an N-terminal amino acid. There is no enzymic conversion ofGlu to pGlu known to date. Moreover, spontaneous cyclization ofGlu-peptides to pGlu-peptides has not been observed as yet. Thereforeone aspect of the present invention was to determine the role of QC inAlzheimer's disease and Down Syndrome. This aspect was addressed by thesynthesis of Aβ3-11 and Aβ1-11, containing the amino acid glutamineinstead of glutamic acid at position three, the determination of thesubstrate characteristics of these modified amyloid β-peptides againstQC, DP IV and DP IV-like enzymes and aminopeptidases and the use ofinhibitors of QC to prevent the formation of pGlu from a N-terminalglutaminyl residue of the amyloid β-derived peptides 1-11 and 3-11. Theresults are shown in example 8. The applied method is described inexample 3.

To date, there are no hints indicating an involvement of QC in theprogression of the disease, because glutamic acid is the N-terminalamino acid in Aβ (3-40/42, or 11-40/42). But, QC is the only knownenzyme capable of forming pGlu at the N-terminus of peptides. Otheraspects of the present invention concern the following findings anddiscoveries:

-   -   a) In a side reaction, QC catalyzes the cyclization of glutamic        acid to pyroglutamic acid at very low rates,    -   b) Glutamic acid of APP or its subsequently formed        amyloid-β-peptides is converted into glutamine        post-translationally by an unknown enzymatic activity and in a        second step, QC catalyzes the cyclization of glutamine into        pyroglutamic acid after processing of the amyloid β-peptide        N-terminus,    -   c) Glutamic acid is converted into glutamine        post-translationally by a chemical catalysis or autocatalysis        and subsequently, QC catalyzes the cyclization of glutamine to        pyroglutamic acid after processing of the amyloid β-peptide        N-terminus,    -   d) There are mutations in the APP gene, which encode the amyloid        β-protein, leading to Gln instead of Glu in position 3. After        translation and processing of the N-terminus, QC catalyzes the        cyclization of glutamine to pyroglutamic acid,    -   e) Glutamine is incorporated into the nascent peptide chain of        APP, due to a malfunction of an unknown enzymatic activity and        subsequently, QC catalyzes the cyclization of N-terminally        glutamine to pyroglutamic acid after processing of the amyloid        β-peptide N-terminus.

QC is involved in the critical step in all five cases listed above,namely the formation of pyroglutamic acid that favors the aggregation ofamyloid β-peptides. Thus, an inhibition of QC leads to a prevention ofthe precipitation of the plaque-forming Aβ3-40/41/43 or Aβ11-40/41/43,causing the onset and progression of Alzheimer's disease and DownSyndrome, independently of the mechanism by which cyclization occurs.

Glutamate is found in positions 3, 11 and 22 of the amyloid β-peptide.Among them the mutation from glutamic acid (E) to glutamine (Q) inposition 22 (corresponding to amyloid precursor protein APP 693,Swissprot P05067) has been described as the so called Dutch typecerebroarterial amyloidosis mutation.

The β-amyloid peptides with a pyroglutamic acid residue in position 3,11 and/or 22 have been described to be more cytotoxic and hydrophobicthan Aβ1-40/42/43 (Saido T. C. 2000 Medical Hypotheses 54(3): 427-429).

The multiple N-terminal variations can be generated by the β-secretaseenzyme β-site amyloid precursor protein-cleaving enzyme (BACE) atdifferent sites (Huse J. T. et al. 2002 J. Biol. Chem. 277 (18):16278-16284), and/or by aminopeptidase processing. In all cases,cyclization can take place according to a)-e) as described above.

So far, there was no experimental evidence supporting the enzymaticconversion of Glu¹-peptides into pGlu-peptides by an unknown glutamylcyclase (EC) corresponding to pathway a) (Garden, R. W., Moroz, T. P.,Gleeson, J. M., Floyd, P. D., Li, L. J., Rubakhin, S. S., and Sweedler,J. V. (1999) J Neurochem 72, 676-681; Hosoda R. et al. (1998) JNeuropathol Exp Neurol. 57, 1089-1095). To date, no such enzyme activityhas been identified, capable to cyclize Glu¹-peptides which areprotonated N-terminally and possess a negatively charged Glu¹γ-carboxylate moiety under mildly alkaline pH-conditions.

QC-activity against Gln¹-substrates is dramatically reduced below pH7.0. In contrast, it appears that Glu¹-conversion can occur at acidicreaction conditions (Iwatsubo, T., Saido, T. C., Mann, D. M., Lee, V.M., and Trojanowski, J. Q. (1996) Am J Pathol 149, 1823-1830; Russo, C.,Saido, T. C., DeBusk, L. M., Tabaton, M., Gambetti, P., and Teller, J.K. (1977) FEBS Lett 409, 411-416; Russo, C., Salis, S., Dolcini, V.,Venezia, V., Song, X. H., Teller, J. K., and Schettini, G. (2001)Neurobiol Dis 8, 173-180; Tekirian, T. L., Saido, T. C., Markesbery, W.R., Russell, M. J., Wekstein, D. R., Patel, E., and Geddes, J. W. (1998)J Neuropathol Exp Neurol. 57, 76-94; Russo, C., Violani, E., Salis, S.,Venezia, V., Dolcini, V., Damonte, G., Benatti, U., DArrigo, C.,Patrone, E., Carlo, P., and Schettini, G. (2002) J Neurochem 82,1480-1489; Hosoda, R., Saido, T. C., Otvos, L., Jr., Arai, T., Mann, D.M., Lee, V. M., Trojanowski, J. Q., and Iwatsubo, T. (1998) JNeuropathol Exp Neurol. 57, 1089-1095; Garden, R. W., Moroz, T. P.,Gleeson, J. M., Floyd, P. D., Li, L. J., Rubakhin, S. S., and Sweedler,J. V. (1999) J Neurochem 72, 676-681).

According to the present invention it was investigated whether QC isable to recognize and to turnover amyloid-β derived peptides under mildacidic conditions. Therefore, the peptides [Gln³]Aβ1-11a, Aβ3-11a,[Gln³]Aβ3-11a, Aβ3-21a, [Gln³]Aβ3-21a and [Gln³]Aβ3-40 as potentialsubstrates of the enzyme were synthesized and investigated. Thesesequences were chosen for mimicking natural N-terminally andC-terminally truncated [Glu³]Aβ peptides and [Gln³]Aβ peptides whichcould occur due to posttranslational Glu-amidation.

In the present invention it was shown that papaya and human QC catalyzeboth glutaminyl and glutamyl cyclization. Apparently, the primaryphysiological function of QC is to finish hormone maturation inendocrine cells by glutamine cyclization prior or during the hormonesecretion process. Such secretory vesicles are known to be acidic in pH.Thus, a side activity of the enzyme in the narrow pH-range from 5.0 to7.0 could be its newly discovered glutamyl cyclase activity transformingalso Glu-Aβ peptides. However, due to the much slower occurringGlu-cyclization compared to Gln-conversion, it is questionable whetherthe glutamyl cyclization plays a significant physiological role. In thepathology of neurodegenerative disorders, however, the glutamylcyclization is of relevance.

Investigating the pH-dependency of this enzymatic reaction, we foundthat the unprotonated N-terminus was essential for the cyclization ofGln¹-peptides and accordingly that the pK_(a)-value of the substrate wasidentical to the pK_(a)-value for QC-catalysis (see FIG. 17). Thus, QCstabilizes the intramolecular nucleophilic attack of the unprotonatedα-amino moiety on the γ-carbonyl carbon electrophilically activated byamidation (Scheme 1).

In contrast to the monovalent charge present on N-terminal glutaminecontaining peptides, the N-terminal Glu-residue in Glu-containingpeptides is predominantly bivalently charged around neutral pH.Glutamate exhibits pK_(a)-values of about 4.2 and 7.5 for theγ-carboxylic and for the α-amino moiety, respectively. I.e. at neutralpH and above, although the α-amino nitrogen is in part or fullyunprotonated and nucleophilic, the γ-carboxylic group is unprotonated,and so exercising no electrophilic carbonyl activity. Hence,intramolecular cyclization is impossible. However, in the pH-range ofabout 5.2-6.5, between their respective pK_(a)-values, the twofunctional groups are present both in non-ionized forms, inconcentrations of about 1-10% (—NH₂) or 10-1% (—COOH) of totalN-terminal Glu-containing peptide. As a result, over a mildly acidicpH-range species of N-terminal Glu-peptides are present which carry bothgroups uncharged, and, therefore, it is possible that QC could stabilizethe intermediate of intramolecular cyclization to pGlu-peptide. I.e. ifthe γ-carboxylic group is protonated, the carbonyl carbon iselectrophilic enough to allow nucleophilic attack by the unprotonatedα-amino group. At this pH the hydroxyl ion functions as a leaving group(Scheme 3). These assumptions are corroborated by the pH-dependence dataobtained for the QC catalyzed conversion of Glu-βNA (see example 11). Incontrast to glutamine conversion of Gln-βNA by QC, the pH-optimum ofcatalysis shifts to the acidic range around pH 6.0, i.e. the pH-range,in which substrate molecule species are simultaneously abundant carryinga protonated γ-carboxyl and unprotonated α-amino group. Furthermore, thekinetically determined pK_(a)-value of 7.55±0.02 is in excellentagreement with that of the α-amino group of Glu-βNA, determined bytitration (7.57±0.05).

Physiologically, at pH 6.0 the second-order rate constant (orspecificity constant, k_(cat)/K_(M)) of the QC-catalyzed glutamatecyclization might be in the range of 8,000 fold slower than the one forglutamine cyclization (FIG. 17). However, the nonenzymatic turnover ofboth model substrates Glu-βNA and Gln-βNA is negligible, being conformwith the observed negligible pGlu-peptide formation in the presentinvention. Hence, for the pGlu-formation by QC an acceleration of atleast 10⁸ can be estimated from the ratio of the enzymatic versusnon-enzymatic rate constants (comparing the second-order rate constantsfor the enzyme catalysis with the respective nonenzymatic cyclizationfirst-order rate constants the catalytic proficiency factor is 10⁹-10¹⁰M⁻¹ for the Gln- and the Glu-conversion, respectively). The conclusionfrom these data is, that in vivo only an enzymatic path resultingpGlu-formations seems conceivable.

Since QC is highly abundant in the brain and taking into account thehigh turnover rate of 0.9 min⁻¹ recently found for the maturation of 30μM of (Gln-)TRH-like peptide (Prokai, L., Prokai-Tatrai, K., Ouyang, X.,Kim, H. S., Wu, W. M., Zharikova, A., and Bodor, N. (1999) J Med Chem42, 4563-4571), one can predict a cyclization half-life of about 100hours for an appropriate glutamate-substrate, similar reactionconditions provided. Moreover, given compartmentalization andlocalization of brain QC/EC in the secretory pathway, the actual in vivoenzyme and substrate concentrations and reaction conditions might beeven more favorable for the enzymatic cyclization in the intact cell.And, if N-terminal Glu is transformed to Gln a much more rapidpGlu-formation mediated by QC could be expected. In vitro, bothreactions were suppressed by applying inhibitors of QC/EC-activity(FIGS. 9, 10 and 15).

In summary, the present invention shows that human QC, which is highlyabundant in the brain, is a likely catalyst to the formation of theamyloidogenic pGlu-Aβ peptides from Glu-Aβ and Gln-Aβ precursors whichmake up more than 50% of the plaque deposits found in Alzheimer'sDisease. These findings identify QC/EC as a player in senile plaqueformation and thus as a novel drug target in the treatment ofAlzheimer's Disease.

In a second embodiment of the present invention, it was found thatamyloid β-derived peptides are a substrate of dipeptidyl peptidase IV(DP IV) or DP IV-like enzymes, preferably dipeptidyl peptidase II(DPII). DP IV, DP II or other DP IV-like enzymes release a dipeptidefrom the N-terminus of the modified amyloid β-peptide (1-11) generatingamyloid β-peptide (3-11) with glutamine as the N-terminal amino acidresidue. The results are shown in example 8.

Prior to cleavage by DP II, DPIV or other DP IV-like enzymes, thepeptide bond between aspartic acid (residue 1 of amyloid β-peptide) andalanine (residue 2 of amyloid β-peptide) may be isomerised yielding anisoaspartyl residue as described in the literature (Kuo, Y.-M.,Emmerling, M. R., Woods, A. S., Cotter, R. J., Roher, A. E. (1997) BBRC237, 188-191; Shimizu, T., Watanabe, A., Ogawara, M., Mori, H. andShirasawa, T. (2000) Arch. Biochem. Biophys. 381, 225-234).

These isoaspartyl residues render the amyloid β-peptide resistantagainst aminopeptidase degradation and consequently the core plaquescontain high amounts of isoAsp¹-amyloid β-peptides, which suggests areduced turnover at the N-terminus.

However, in the present invention it is demonstrated for the first time,that the N-terminal dipeptide H-isoAsp¹-Ala²-OH can be released bydipeptidyl peptidases especially under acidic conditions. Furthermore,it was shown that isomerization can precede also cleavage byβ-secretase, and that isomerization may accelerate proteolyticprocessing, thus leading to liberation of an N-terminal isoaspartyl bondof isoAsp¹-amyloid β-peptides which subsequently is subject to turnoverby DP II, DPIV or DP IV-like enzymes (Momand, J. and Clarke, S. (1987)Biochemistry 26, 7798-7805; Kuo, Y.-M., Emmerling, M. R., Woods, A. S.,Cotter, R. J., Roher, A. E. (1997) BBRC 237, 188-191). Accordingly,inhibition of isoaspartyl formation may lead to the reduction ofcleavage by β-secretase and, in turn, to a reduced formation of amyloidβ-peptides. In addition, blockage of the isoAsp¹-amyloid β-peptideturnover by inhibition of DP II, DPIV or DP IV-like enzymes wouldprevent the exposure of [Glu³]Aβ to QC/EC-catalyzed formation of[pGlu³]Aβ.

In a third embodiment of the present invention, a combination ofinhibitors of DP IV-activity and of inhibitors of QC can be used for thetreatment of Alzheimer's disease and Down Syndrome.

The combined effect of DP IV and/or DP IV-like enzymes and of QC isillustrated as follows:

-   -   a) DP IV and/or DP IV-like enzymes cleave Aβ1-40/42, a dipeptide        comprising H-Asp-Ala-OH and Aβ3-40/42 are released,    -   b) In a side reaction, QC catalyzes the cyclization of glutamic        acid to pyroglutamic acid at very low rates,    -   c) Glutamic acid is converted into glutamine at the N-terminus        post-translationally by an unknown enzymatic activity and        subsequently, QC catalyzes the cyclization of glutamine into        pyroglutamic acid after processing of the amyloid β-peptide        N-terminus,    -   d) Glutamic acid is converted into glutamine        post-translationally by a chemical catalysis or autocatalysis        and in a second step, QC catalyzes the cyclization of glutamine        into pyroglutamic acid after processing of the amyloid β-peptide        N-terminus,    -   e) There are mutations in the APP gene, which encode the amyloid        β-protein, leading to Gln instead of Glu in position 3 of Aβ,        After translation and processing of the N-terminus, QC catalyzes        the cyclization of glutamine to pyroglutamic acid,    -   f) Glutamine is incorporated into the nascent peptide chain of        APP, due to a malfunction of an unknown enzymatic activity and        subsequently, QC catalyzes the cyclization of N-terminally        glutamine to pyroglutamic acid after processing of the amyloid        β-peptide N-terminus,

The N-terminal Gln-exposure to QC-activity can be also triggered bydifferent peptidase activities. Aminopeptidases can remove sequentiallyAsp and Ala from the N-terminus of Aβ1-40/41/43, thus unmasking aminoacid three that is prone to cyclization. Dipeptidyl peptidases, such asDP I, DP II, DP IV, DP 8, DP 9 and DP 10, remove the dipeptide Asp-Alain one step. Hence, inhibition of aminopeptidase- ordipeptidylpeptidase-activity is useful to prevent the formation ofAβ3-40/41/43.

The combined effect of inhibitors of DP IV and/or DP IV-like enzymes andof activity lowering effectors of QC is illustrated in the followingway:

-   -   a) The inhibitors of DP IV and/or DP IV-like enzymes inhibit the        conversion of Aβ1-40/42 to Aβ3-40/42.    -   b) An N-terminal exposure of glutamic acid is thereby prevented        and no conversion to glutamine, either by enzymatic or by        chemical catalysis, subsequently leading to pyroglutamic acid        formation, is possible.    -   c) Inhibitors of QC prevent in addition the formation        pyroglutamic acid from any residual modified Aβ3-40/42 molecules        and those modified Aβ3-40/42 molecules, which are generated by        mutations of the APP gene.

Within the present invention, a similar combined action of DP IV or DPIV-like enzymes and QC was demonstrated for further peptide hormones,such as glucagon, CC chemokines and substance P.

Glucagon is a 29-amino acid polypeptide released from pancreatic isletalpha-cells that acts to maintain euglycemia by stimulating hepaticglycogenolysis and gluconeogenesis. Despite its importance, thereremains controversy about the mechanisms responsible for glucagonclearance in the body. Pospisilik et al. assessed the enzymaticmetabolism of glucagon using sensitive mass spectrometric techniques toidentify the molecular products. Incubation of glucagon with purifiedporcine dipeptidyl peptidase IV (DP IV) yielded sequential production ofglucagon3-29 and glucagon5-29. In human serum, degradation toglucagon3-29 was rapidly followed by N-terminal cyclization of glucagon,preventing further DP IV-mediated hydrolysis. Bioassay of glucagon,following incubation with purified DP IV or normal rat serumdemonstrated a significant loss of hyperglycemic activity, while asimilar incubation in DP IV-deficient rat serum did not show any loss ofglucagon bioactivity. Degradation, monitored by mass spectrometry andbioassay, was blocked by the specific DP IV inhibitor, isoleucylthiazolidine. These results identify DP IV as a primary enzyme involvedin the degradation and inactivation of glucagon. These findings haveimportant implications for the determination of glucagon levels in humanplasma (Pospisilik et al., Regul Pept 2001 Jan. 12;96(3):133-41).

Human Monocyte Chemotactic Protein (MCP)-2 has originally been isolatedfrom stimulated osteosarcoma cells as a chemokine coproduced with MCP-1and MCP-3. Von Coillie et al. (Van Coillie, E. et al. 1998 Biochemistry37, 12672-12680) cloned a 5′-end extended MCP-2 cDNA from a human testiscDNA library. It encoded a 76 residue MCP-2 protein, but differed fromthe reported bone marrow-derived MCP-2 cDNA sequence in codon 46, whichcoded for a Lys instead of a Gln. This MCP-2Lys46 variant, caused by asingle nucleotide polymorphism (SNP), was biologically compared withMCP-2Gln46. The coding regions were sub-cloned into the bacterialexpression vector pHEN1, and after transformation of Escherichia coli,the two MCP-2 protein variants were recovered from the periplasm. Edmandegradation revealed a Gln residue at the NH₂ terminus instead of apGlu. rMCP-2Gln46 and rMCP-2Lys46 and the NH₂-terminal cycliccounterparts were tested on monocytic cells in calcium mobilization andchemotaxis assays. No significant difference in biological activity wasobserved between the rMCP-2Gln46 and rMCP-2Lys46 isoforms. However, forboth MCP-2 variants the NH₂-terminal pyroglutamate was shown to beessential for chemotaxis, but not for calcium mobilization. NH₂-terminaltruncation of rMCP-2Lys46 by the serine protease CD26/dipeptidylpeptidase IV (CD26/DPP IV) resulted in the release of the NH₂-terminalGln-Pro dipeptide, whereas synthetic MCP-2 with an amino-terminal pGluremained unaffected. CD26/DPP IV-clipped rMCP-2Lys46(3-76) was almostcompletely inactive in both chemotaxis and signaling assays. Theseobservations indicated that the NH₂-terminal pGlu in MCP-2 is necessaryfor chemotactic activity but also that it protects the protein againstdegradation by CD26/DPP IV (van Coillie, E. et al. Biochemistry 1998 37,12672-80).

Within the present invention, it was determined by LC/MS-analysis thatthe formation of the N-terminal pyroglutamate residue determined inglucagon3-29 (Pospisilik et al., 2001), and in MCP-2 isoforms (vanCoillie et al., 1998), is catalyzed by QC.

In addition, it was proven by LC/MS-investigation that after N-terminalDP IV-catalyzed removal of the two dipeptides Lys-Pro and Arg-Pro fromsubstance P the remaining [Gln⁵]substance P5-11 is transformed by QC to[pGlu⁵]substance P5-11.

DP IV inhibitors are disclosed in WO 99/61431. In particular, DP IVinhibitors are disclosed comprising an amino acid residue and athiazolidine or pyrrolidine group, and salts thereof, especiallyL-threo-isoleucyl thiazolidine, L-allo-isoleucyl thiazolidine,L-threo-isoleucyl pyrrolidine, L-allo-isoleucyl thiazolidine,L-allo-isoleucyl pyrrolidine, and salts thereof.

Further examples of low molecular weight dipeptidyl peptidase IVinhibitors are agents such as tetrahydroisoquinolin-3-carboxamidederivatives, N-substituted 2-cyanopyroles and -pyrrolidines,N-(N′-substituted glycyl)-2-cyanopyrrolidines, N-(substitutedglycyl)-thiazolidines, N-(substituted glycyl)-4-cyanothiazolidines,amino-acyl-borono-prolyl-inhibitors, cyclopropyl-fused pyrrolidines andheterocyclic compounds. Inhibitors of dipeptidyl peptidase IV aredescribed in U.S. Pat. No. 6,380,398, U.S. Pat. No. 6,011,155; U.S. Pat.No. 6,107,317; U.S. Pat. No. 6,110,949; U.S. Pat. No. 6,124,305; U.S.Pat. No. 6,172,081; WO 95/15309, WO 99/61431, WO 99/67278, WO 99/67279,DE 198 34 591, WO 97/40832, DE 196 16 486 C 2, WO 98/19998, WO 00/07617,WO 99/38501, WO 99/46272, WO 99/38501, WO 01/68603, WO 01/40180, WO01/81337, WO 01/81304, WO 01/55105, WO 02/02560 and WO 02/14271, WO02/04610, WO 02/051836, WO 02/068420, WO 02/076450; WO 02/083128, WO02/38541, WO 03/000180, WO 03/000181, WO 03/000250, WO 03/002530, WO03/002531, WO 03/002553, WO 03/002593, WO 03/004496, WO 03/024942 and WO03/024965, the teachings of which are herein incorporated by referencein their entirety, especially concerning these inhibitors, theirdefinition, uses and their production.

Preferred for the use in combination with effectors of QC are DPIVinhibitors such as NVP-DPP728A(1-[[[2-[{5-cyanopyridin-2-yl}amino]ethyl]amino]acetyl]-2-cyano-(S)-pyrrolidine)(Novartis) as disclosed by Hughes et al. 1999 Biochemistry 3811597-11603, LAF-237(1-[(3-hydroxy-adamant-1-ylamino)-acetyl]-pyrrolidine-2(S)-carbonitrile);disclosed by Hughes et al., Meeting of the American Diabetes Association2002, Abstract no. 272 (Novartis), TSL-225(tryptophyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid), disclosedby Yamada et al. 1998 Bioorg Med Chem Lett 8, 1537-1540,2-cyanopyrrolidides and 4-cyanopyrrolidides as disclosed by Asworth etal. 1996 Bioorg Med Chem Lett 6, 1163-1166 and 2745-2748, FE-999011,disclosed by Sudre et al. 2002 Diabetes 51, 1461-1469 (Ferring) and thecompounds disclosed in WO 01/34594 (Guilford), employing dosages as setout in the above references.

More preferred DP IV inhibitors for the use in combination witheffectors of QC are dipeptide compounds in which the amino acid ispreferably selected from a natural amino acid, such as, for example,leucine, valine, glutamine, glutamic acid, proline, isoleucine,asparagines and aspartic acid. The dipeptide-like compounds usedaccording to the invention exhibit at a concentration (of dipeptidecompounds) of 10 μM, a reduction in the activity of plasma dipeptidylpeptidase IV or DPIV-analogous enzyme activities of at least 10%,especially of at least 40%. Frequently a reduction in activity of atleast 60% or at least 70% is also desired in vivo. Preferred compoundsmay also exhibit a reduction in activity of a maximum of 20% or 30%.

Preferred dipeptide compounds are N-valyl prolyl, O-benzoylhydroxylamine, alanyl pyrrolidine, isoleucyl thiazolidine likeL-allo-isoleucyl thiazolidine, L-threo-isoleucyl pyrrolidine and saltsthereof, especially the fumaric salts, and L-allo-isoleucyl pyrrolidineand salts thereof. Especially preferred compounds are glutaminylpyrrolidine and glutaminyl thiazolidine, H-Asn-pyrrolidine,H-Asn-thiazolidine, H-Asp-pyrrolidine, H-Asp-thiazolidine,H-Asp(NHOH)-pyrrolidine, H-Asp(NHOH)-thiazolidine, H-Glu-pyrrolidine,H-Glu-thiazolidine, H-Glu(NHOH)-pyrrolidine, H-Glu(NHOH)-thiazolidine,H-His-pyrrolidine, H-His-thiazolidine, H-Pro-pyrrolidine,H-Pro-thiazolidine, H-Ile-azididine, H-Ile-pyrrolidine,H-L-allo-Ile-thiazolidine, H-Val-pyrrolidine and H-Val-thiazolidine andpharmaceutically acceptable salts thereof. These compounds are describedin WO 99/61431 and EP 1 304 327.

Furthermore, the present invention provides for the use of effectors ofQC in combination with substrate-like peptide compounds useful forcompetitive modulation of dipeptidyl peptidase IV catalysis. Preferredpeptide compounds are 2-Amino octanoic acid-Pro-Ile, Abu-Pro-Ile,Aib-Pro-Ile, Aze-Pro-Ile, Cha-Pro-Ile, Ile-Hyp-Ele, Ile-Pro-allo-Ile,Ile-Pro-t-butyl-Gly, Ile-Pro-Val, Nle-Pro-Ile, Nva-Pro-Ile, Orn-Pro-Ile,Phe-Pro-Ile, Phg-Pro-Ile, Pip-Pro-Ile, Ser(Bzl)-Pro-Ile, Ser(P)-Pro-Ile,Ser-Pro-Ile, t-butyl-Gly-Pro-D-Val, t-butyl-Gly-Pro-Gly,t-butyl-Gly-Pro-Ile, t-butyl-Gly-Pro-Ile-amide,t-butyl-Gly-Pro-t-butyl-Gly, t-butyl-Gly-Pro-Val, Thr-Pro-Ile,Tic-Pro-Ile, Trp-Pro-Ile, Tyr(P)-Pro-Ile, Tyr-Pro-allo-Ile,Val-Pro-allo-Ile, Val-Pro-t-butyl-Gly, Val-Pro-Val and pharmaceuticallyacceptable salts thereof, wherein t-butyl-Gly is defined as

and Ser(Bzl) and Ser(P) are defined as benzyl-serine andphosphoryl-serine, respectively. Tyr(P) is defined asphosphoryl-tyrosine. These compounds are disclosed in WO 03/002593.

Further preferred DP IV-inhibitors, which can be used according to thepresent invention in combination with effectors of QC, arepeptidylketones, e.g.

-   2-Methylcarbonyl-1-N-[(L)-Alanyl-(L)-Valinyl]-(2S)-pyrrolidine    hydrobromide,    2-Methyl)carbonyl-1-N-[(L)-Valinyl-(L)-Prolyl-(L)-Valinyl]-(2S)-pyrrolidine    hydrobromide,-   2-[(Acetyl-oxy-methyl)carbonyl]-1-N-[(L)-Alanyl-(L)-Valinyl]-(2S)-pyrrolidine    hydrobromide,-   2-[Benzoyl-oxy-methyl)carbonyl]-1-N-[{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidine    hydrobromide,-   2-{[(2,6-Dichlorbenzyl)thiomethyl]carbonyl    }-1-N-[{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidine,-   2-[Benzoy-loxy-methyl)carbonyl]-1-N-[Glycyl-(L)-Valinyl]-(2S)-pyrrolidine    hydrobromide,-   2-[([1,3]-Thiazolethiazol-2-yl)carbonyl]-1-N-[{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidine    trifluoracetate,-   2-[(Benzothiazolethiazol-2-yl)carbonyl]-1-N-[N-{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidin    trifluoracetate,-   2-[(-Benzothiazolethiazol-2-yl)carbonyl]-1-N-[{(L)-Alanyl}-Glycyl]-(2S)-pyrrolidine    trifluoracetate,-   2-[(Pyridin-2-yl)carbonyl]-1-N-[N-{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidine    trifluoracetate    and other pharmaceutically acceptable salts thereof. These compounds    are disclosed in WO 03/033524.

Further, according to the present invention substituted aminoketones canbe used in combination with effectors of QC. Preferred substitutedaminoketones are

-   1-cyclopentyl-3-methyl-1-oxo-2-pentanaminium chloride,-   1-cyclopentyl-3-methyl-1-oxo-2-butanaminium chloride,-   1-cyclopentyl-3,3-dimethyl-1-oxo-2-butanaminium chloride,-   1-cyclohexyl-3,3-dimethyl-1-oxo-2-butanaminium chloride,-   3-(cyclopentylcarbonyl)-1,2,3,4-tetrahydroisoquinolinium chloride,-   N-(2-cyclopentyl-2-oxoethyl)cyclohexanaminium chloride    and other pharmaceutically acceptable salts thereof.

Among the rare group of proline-specific proteases, DP IV was originallybelieved to be the only membrane-bound enzyme specific for proline asthe penultimate residue at the amino-terminus of the polypeptide chain.However, other molecules, even those structurally non-homologous withthe DP IV but bearing corresponding enzyme activity, have beenidentified. DP IV-like enzymes, which have been identified so far,include e.g. fibroblast activation protein α, dipeptidyl peptidase IV β,dipeptidyl aminopeptidase-like protein, N-acetylated α-linked acidicdipeptidase, quiescent cell proline dipeptidase, dipeptidyl peptidaseII, attractin and dipeptidyl peptidase IV related protein (DPP 8), DPL1(DPX, DP6), DPL2 and DPP 9 described in review articles by Sedo & Malik(Sedo and Malik 2001, Biochim Biophys Acta, 36506, 1-10) and Abbott andGorrell (Abbott, C. A. and Gorrell, M. D. 2002 In: Langner & Ansorge(ed.), Ectopeptidases. Kluwer Academic/Plenum Publishers, New York,171-195). Recently, the cloning and characterization of dipeptidylpeptidase 10 (DPP 10) was reported (Qi, S. Y. et al., BiochemicalJournal Immediate Publication. Published on 28 Mar. 2003 as manuscriptBJ20021914).

Effectors, as that term is used herein, are defined as molecules thatbind to enzymes and increase or decrease their activity in vitro and/orin vivo. Some enzymes have binding sites for small molecules that affecttheir catalytic activity; a stimulator molecule is called an activator.Enzymes may even have multiple sites for recognizing more than oneactivator or inhibitor. Enzymes can detect concentrations of a varietyof molecules and use that information to vary their own activities.

Effectors can modulate enzymatic activity because enzymes can assumeboth active and inactive conformations: activators are positiveeffectors, inhibitors are negative effectors. Effectors act not only atthe active sites of enzymes, but also at regulatory sites, or allostericsites, terms used to emphasize that the regulatory site is an element ofthe enzyme distinct from the catalytic site and to differentiate thisform of regulation from competition between substrates and inhibitors atthe catalytic site (Darnell, J., Lodish, H. and Baltimore, D. 1990,Molecular Cell Biology 2^(nd) Edition, Scientific American Books, NewYork, page 63).

In the peptides of the present invention, each amino acid residue isrepresented by a one-letter or a three-letter designation, correspondingto the trivial name of the amino acid, in accordance with the followingconventional list:

One-Letter Three-Letter Amino Acid Symbol Symbol Alanine A Ala ArginineR Arg Asparagine N Asn Aspartic acid D Asp Cysteine C Cys Glutamine QGln Glutamic acid E Glu Glycine G Gly Histidine H His Isoleucine I IleLeucine L Leu Lysine K Lys Methionine M Met Phenylalanine F Phe ProlineP Pro Serine S Ser Threonine T Thr Tryptophan W Trp Tyrosine Y TyrValine V Val

The term “QC” as used herein comprises glutaminyl cyclase (QC) andQC-like enzymes. QC and QC-like enzymes have identical or similarenzymatic activity, further defined as QC activity. In this regard,QC-like enzymes can fundamentally differ in their molecular structurefrom QC.

The term “QC activity” as used herein is defined as intramolecularcyclization of N-terminal glutamine residues into pyroglutamic acid(pGlu*) or of N-terminal L-homoglutamine or L-β-homoglutamine to acyclic pyro-homoglutamine derivative under liberation of ammonia. Seetherefore schemes 1 and 2.

The term “EC” as used herein comprises the side activity of QC andQC-like enzymes as glutamate cyclase (EC), further defined as ECactivity.

The term “EC activity” as used herein is defined as intramolecularcyclization of N-terminal glutamate residues into pyroglutamic acid(pGlu*) by QC. See therefore scheme 3.

The term “metal-dependent enzyme” as used herein is defined as enzyme(s)that require a bound metal ion in order to fulfill their catalyticfunction and/or require a bound metal ion in order to form thecatalytically active structure.

Molecules that bind to enzymes and increase or decrease their activitiesare called “effectors”. Effectors can modify enzymatic activity becauseenzymes can assume both active and inactive conformations: activatorsare positive effectors; inhibitors are negative effectors. Effectorsbind at regulatory sites, or allosteric sites (from the Greek for“another shape”), a term used to emphasize that the regulatory site isan element of the enzyme distinct from the catalytic site and todifferentiate this form of regulation from competition betweensubstrates and inhibitors at the catalytic site.

According to the individual embodiments of the present invention, eitheractivators or inhibitors are preferred.

Another aspect of the present invention is the identification of newphysiological substrates of QC. These were identified by performingcyclization experiments with mammalian peptides as described in example5. Prior, human QC and papaya QC were isolated as described inexample 1. The applied methods are described in example 2, and thepeptide synthesis employed is outlined in example 6. The results of thestudy are shown in Table 1.

TABLE 1 New physiological substrates of glutaminyl cyclase (*,determined qualitatively by MALDI-TOF experiments) Human QC Papaya QCk_(cat) k_(cat)/K_(M) k_(cat) k_(cat)/K_(M) Substrate K_(M) (μM) (s⁻¹)(mM⁻¹ s⁻¹) K_(M) (μM) (s⁻¹) (mM⁻¹ s⁻¹) [Gln¹]-Gastrin 31 ± 1  54.1 ±0.6  1745.2 ± 36.9  34 ± 2  25.8 ± 0.5  759 ± 30  [Gln¹]- 37 ± 1  48.8 ±0.4  1318.9 ± 24.8  40 ± 3  35.7 ± 0.9  893 ± 44  Neurotensin [Gln¹]-FPP87 ± 2  69.6 ± 0.3  800.0 ± 14.9  232 ± 9  32.5 ± 0.4  140 ± 4 [Gln¹]-TRH 90 ± 4  82.8 ± 1.2  920.0 ± 27.6  n.d. n.d. n.d. [Gln¹]-GnRH53 ± 3  69.2 ± 1.1  1305.7 ± 53.2  169 ± 9  82.5 ± 1.9  488.2 ± 14.8 [Gln³]- * * glucagon(3-29) [Gln⁵]-substance * * P(5-11)

All analyses were performed in the optimal range of activity andstability of either human or plant QC, as demonstrated in example 4.

The amino acid sequences of physiological active peptides having anN-terminal glutamine residue and being therefore substrates for the QCenzyme are listed in Table 2:

TABLE 2 Amino acid sequences of physiological active peptides with anN-terminal glutamine residue Peptide Amino acid sequence FunctionGastrin 17 QGPWL EEEEEAYGWM DF Gastrin stimulates the stomachSwiss-Prot: P01350 (amide) mucosa to produce and secrete hydrochloricacid and the pancreas to secrete its digestive enzymes. It alsostimulates smooth muscle contraction and increases blood circulation andwater secretion in the stomach and intestine. Neurotensin QLYENKPRRP YILNeurotensin plays an endocrine Swiss-Prot: P30990 or paracrine role inthe regulation of fat metabolism. It causes contraction of smoothmuscle. FPP QEP amide A tripeptide related to thyrotrophin releasinghormone (TRH), is found in seminal plasma. Recent evidence obtained invitro and in vivo showed that FPP plays an important role in regulatingsperm fertility. TRH QHP amide TRH functions as a regulator ofSwiss-Prot: P20396 the biosynthesis of TSH in the anterior pituitarygland and as a neurotransmitter/ neuromodulator in the central andperipheral nervous systems. GnRH QHWSYGL RP(G) amide Stimulates thesecretion of Swiss-Prot: P01148 gonadotropins; it stimulates thesecretion of both luteinizing and follicle-stimulating hormones. CCL16(small QPKVPEW VNTPSTCCLK Shows chemotactic activity for induciblecytokine YYEKVLPRRL VVGYRKALNC lymphocytes and monocytes but A16)HLPAIIFVTK RNREVCTNPN not neutrophils. Also shows Swiss-Prot: O15467DDWVQEYIKD PNLPLLPTRN potent myelosuppressive LSTVKIITAK NGQPQLLNSQactivity, suppresses proliferation of myeloid progenitor cells.Recombinant SCYA16 shows chemotactic activity for monocytes and THP-1monocytes, but not for resting lymphocytes and neutrophils. Induces acalcium flux in THP-1 cells that were desensitized by prior expressionto RANTES. CCL8 (small QPDSVSI PITCCFNVIN Chemotactic factor thatattracts inducible cytokine RKIPIQRLES YTRITNIQCP monocytes,lymphocytes, A8) KEAVIFKTKR GKEVCADPKE basophils and eosinophils. MaySwiss-Prot: P80075 RWVRDSMKHL DQIFQNLKP play a role in neoplasia andinflammatory host responses. This protein can bind heparin. CCL2 (smallQPDAINA PVTCCYNFTN Chemotactic factor that attracts inducible cytokineRKISVQRLAS YRRITSSKCP monocytes and basophils but A2) KEAVIFKTIVAKEICADPKQ not neutrophils or eosinophils. Swiss-Prot: P13500 KWVQDSMDHLDKQTQTPKT Augments monocyte anti-tumor activity. Has been implicated inthe pathogenesis of diseases characterized by monocytic infiltrates,like psoriasis, rheumatoid arthritis or atherosclerosis. May be involvedin the recruitment of monocytes into the arterial wall during thedisease process of atherosclerosis. Binds to CCR2 and CCR4. CCL18 (smallQVGTNKELC CLVYTSWQIP Chemotactic factor that attracts inducible cytokineQKFIVDYSET SPQCPKPGVI lymphocytes but not monocytes A18) LLTKRGRQICADPNKKWVQK or granulocytes. May be Swiss-Prot: P55774 YISDLKLNA involvedin B cell migration into B cell follicles in lymph nodes. Attracts naiveT lymphocytes toward dendritic cells and activated macrophages in lymphnodes, has chemotactic activity for naive T cells, CD4+ and CD8+ T cellsand thus may play a role in both humoral and cell-mediated immunityresponses. Fractalkine QHHGVT KCNITCSKMT The soluble form is chemotactic(neurotactin) SKIPVALLIH YQQNQASCGK for T cells and monocytes, butSwiss-Prot: P78423 RAIILETRQH RLFCADPKEQ not for neutrophils. TheWVKDAMQHLD RQAAALTRNG membrane-bound form GTFEKQIGEV KPRTTPAAGG promotesadhesion of those MDESVVLEPE ATGESSSLEP leukocytes to endothelial cells.TPSSQEAQRA LGTSPELPTG May play a role in regulating VTGSSGTRLPPTPKAQDGGP leukocyte adhesion and VGTELFRVPP VSTAATWQSS migrationprocesses at the APHQPGPSLW AEAKTSEAPS endothelium. Binds to cx3cr1.TQDPSTQAST ASSPAPEENA PSEGQRVWGQ GQSPRPENSL EREEMGPVPA HTDAFQDWGPGSMAHVSVVP VSSEGTPSRE PVASGSWTPK AEEPIHATMD PQRLGVLITP VPDAQAATRRQAVGLLAFLG LLFCLGVAMF TYQSLQGCPR KMAGEMAEGL RYIPRSCGSN SYVLVPV CCL7(small QPVGINT STTCCYRFIN Chemotactic factor that attracts induciblecytokine KKIPKQRLES YRRTTSSHCP monocytes and eosinophils, but A7)REAVIFKTKL DKEICADPTQ not neutrophils. Augments Swiss-Prot: P80098KWVQDFMKHL DKKTQTPKL monocyte anti-tumor activity. Also induces therelease of gelatinase B. This protein can bind heparin. Binds to CCR1,CCR2 and CCR3. Orexin A QPLPDCCRQK TCSCRLYELL Neuropeptide that plays a(Hypocretin-1) HGAGNHAAGI LTL significant role in the regulationSwiss-Prot O43612 of food intake and sleep- wakefulness, possibly bycoordinating the complex behavioral and physiologic responses of thesecomplementary homeostatic functions. It plays also a broader role in thehomeostatic regulation of energy metabolism, autonomic function,hormonal balance and the regulation of body fluids. Orexin-A binds toboth OX1R and OX2R with a high 7affinity. Substance P RPK PQQFFGLMBelongs to the tachykinins. Tachykinins are active peptides which exciteneurons, evoke behavioral responses, are potent vasodilators andsecretagogues, and contract (directly or indirectly) many smoothmuscles.

In a fourth embodiment, the peptides [Gln¹]Gastrin (17 and 34 aminoacids in length), [Gln¹]Neurotensin and [Gln¹]FPP were identified as newphysiological substrates of QC. Gastrin, Neurotensin and FPP comprise apGlu residue in their N-terminal position. This N-terminal pGlu residuewas shown to be formed from N-terminal glutamine by QC catalysis for allpeptides. As a result, these peptides are activated in terms of theirbiological function upon conversion of the N-terminal glutamine residueto pGlu.

Transepithelial transducing cells, particularly the gastrin (G) cell,co-ordinate gastric acid secretion with the arrival of food in thestomach. Recent work showed that multiple active products are generatedfrom the gastrin precursor, and that there are multiple control pointsin gastrin biosynthesis. Biosynthetic precursors and intermediates(progastrin and Gly-gastrins) are putative growth factors; theirproducts, the amidated gastrins, regulate epithelial cell proliferation,the differentiation of acid-producing parietal cells andhistamine-secreting enterochromaffin-like (ECL) cells, and theexpression of genes associated with histamine synthesis and storage inECL cells, as well as acutely stimulating acid secretion. Gastrin alsostimulates the production of members of the epidermal growth factor(EGF) family, which in turn inhibit parietal cell function but stimulatethe growth of surface epithelial cells. Plasma gastrin concentrationsare elevated in subjects with Helicobacter pylori, who are known to haveincreased risk of duodenal ulcer disease and gastric cancer (Dockray, G.J. 1999 J Physiol 15 315-324).

The peptide hormone gastrin, released from antral G cells, is known tostimulate the synthesis and release of histamine from ECL cells in theoxyntic mucosa via CCK-2 receptors. The mobilized histamine induces acidsecretion by binding to the H(2) receptors located on parietal cells.Recent studies suggest that gastrin, in both its fully amidated and lessprocessed forms (progastrin and glycine-extended gastrin), is also agrowth factor for the gastrointestinal tract. It has been establishedthat the major trophic effect of amidated gastrin is for the oxynticmucosa of stomach, where it causes increased proliferation of gastricstem cells and ECL cells, resulting in increased parietal and ECL cellmass. On the other hand, the major trophic target of the less processedgastrin (e.g. glycine-extended gastrin) appears to be the colonic mucosa(Koh, T. J. and Chen, D. 2000 Regul Pept 9337-44).

In a fifth embodiment, the present invention provides the use ofactivity increasing effectors of QC for the stimulation ofgastrointestinal tract cell proliferation, especially gastric mucosalcell proliferation, epithelial cell proliferation, the differentiationof acid-producing parietal cells and histamine-secretingenterochromaffin-like (ECL) cells, and the expression of genesassociated with histamine synthesis and storage in ECL cells, as well asfor the stimulation of acute acid secretion in mammals by maintaining orincreasing the concentration of active [pGlu¹]-Gastrin.

In a sixth embodiment, the present invention provides the use ofactivity decreasing effectors of QC for the treatment of duodenal ulcerdisease and gastric cancer with or w/o Heliobacter pylori in mammals bydecreasing the conversion rate of inactive [Gln¹]Gastrin to active[pGlu¹]Gastrin.

Neurotensin (NT) is a neuropeptide implicated in the pathophysiology ofschizophrenia that specifically modulates neurotransmitter systemspreviously demonstrated to be misregulated in this disorder. Clinicalstudies in which cerebrospinal fluid (CSF) NT concentrations have beenmeasured revealed a subset of schizophrenic patients with decreased CSFNT concentrations that are restored by effective antipsychotic drugtreatment. Considerable evidence also exists concordant with theinvolvement of NT systems in the mechanism of action of antipsychoticdrugs. The behavioral and biochemical effects of centrally administeredNT remarkably resemble those of systemically administered antipsychoticdrugs, and antipsychotic drugs increase NT neurotransmission. Thisconcatenation of findings led to the hypothesis that NT functions as anendogenous antipsychotic. Moreover, typical and atypical antipsychoticdrugs differentially alter NT neurotransmission in nigrostriatal andmesolimbic dopamine terminal regions, and these effects are predictiveof side effect liability and efficacy, respectively (Binder, E. B. etal. 2001 Biol Psychiatry 50 856-872).

In a seventh embodiment, the present invention provides the use ofactivity increasing effectors of QC for the preparation of antipsychoticdrugs and/or for the treatment of schizophrenia in mammals. Theeffectors of QC either maintain or increase the concentration of active[pGlu¹]neurotensin.

Fertilization promoting peptide (FPP), a tripeptide related tothyrotrophin releasing hormone (TRH), is found in seminal plasma. Recentevidence obtained in vitro and in vivo showed that FPP plays animportant role in regulating sperm fertility. Specifically, FPPinitially stimulates nonfertilizing (uncapacitated) spermatozoa to“switch on” and become fertile more quickly, but then arrestscapacitation so that spermatozoa do not undergo spontaneous acrosomeloss and therefore do not lose fertilizing potential. These responsesare mimicked, and indeed augmented, by adenosine, known to regulate theadenylyl cyclase (AC)/cAMP signal transduction pathway. Both FPP andadenosine have been shown to stimulate cAMP production in uncapacitatedcells but inhibit it in capacitated cells, with FPP receptors somehowinteracting with adenosine receptors and G proteins to achieveregulation of AC. These events affect the tyrosine phosphorylation stateof various proteins, some being important in the initial “switching on,”others possibly being involved in the acrosome reaction itself.Calcitonin and angiotensin II, also found in seminal plasma, havesimilar effects in vitro on uncapacitated spermatozoa and can augmentresponses to FPP. These molecules have similar effects in vivo,affecting fertility by stimulating and then maintaining fertilizingpotential. Either reductions in the availability of FPP, adenosine,calcitonin, and angiotensin II or defects in their receptors contributeto male infertility (Fraser, L. R. and Adeoya-Osiguwa, S. A. 2001 VitamHorm 63, 1-28).

In an eight embodiment, the present invention provides the use ofactivity lowering effectors of QC for the preparation of fertilizationprohibitive drugs and/or to reduce the fertility in mammals. Theactivity lowering effectors of QC decrease the concentration of active[pGlu¹]FPP, leading to a prevention of sperm capacitation anddeactivation of sperm cells. In contrast it could be shown that activityincreasing effectors of QC are able to stimulate fertility in males andto treat infertility.

In a ninth embodiment, further physiological substrates of QC wereidentified within the present invention. These are [Gln¹]CCL2,[Gln¹]CCL7, [Gln¹]CCL8, [Gln¹]CCL16, [Gln¹]CCL18 and [Gln¹]fractalkine.For details see Table 2. These polypeptides play an important role inpathophysiological conditions, such as suppression of proliferation ofmyeloid progenitor cells, neoplasia, inflammatory host responses,cancer, psoriasis, rheumatoid arthritis, atherosclerosis, humoral andcell-mediated immunity responses, leukocyte adhesion and migrationprocesses at the endothelium.

Several cytotoxic T lymphocyte peptide-based vaccines against hepatitisB, human immunodeficiency virus and melanoma were recently studied inclinical trials. One interesting melanoma vaccine candidate alone or incombination with other tumor antigens, is the decapeptide ELA. Thispeptide is a Melan-A/MART-1 antigen immunodominant peptide analog, withan N-terminal glutamic acid. It has been reported that the amino groupand gamma-carboxylic group of glutamic acids, as well as the amino groupand gamma-carboxamide group of glutamines, condense easily to formpyroglutamic derivatives. To overcome this stability problem, severalpeptides of pharmaceutical interest have been developed with apyroglutamic acid instead of N-terminal glutamine or glutamic acid,without loss of pharmacological properties. Unfortunately compared withELA, the pyroglutamic acid derivative (PyrELA) and also the N-terminalacetyl-capped derivative (AcELA) failed to elicit cytotoxic T lymphocyte(CTL) activity. Despite the apparent minor modifications introduced inPyrELA and AcELA, these two derivatives probably have lower affinitythan ELA for the specific class I major histocompatibility complex.Consequently, in order to conserve full activity of ELA, the formationof PyrELA must be avoided (Beck A. et al. 2001, J Pept Res57(6):528-38.). Recently, it was found that also the enzyme glutaminylcyclase (QC) is overexpressed in melanomas (Ross D. T et al., 2000, NatGenet 24:227-35.).

In a tenth embodiment, the present invention provides the use ofeffectors of QC for the preparation of a medicament for the treatment ofpathophysiological conditions, such as suppression of proliferation ofmyeloid progenitor cells, neoplasia, inflammatory host responses,cancer, malign metastasis, melanoma, psoriasis, rheumatoid arthritis,atherosclerosis, impaired humoral and cell-mediated immunity responses,leukocyte adhesion and migration processes at the endothelium.

In an eleventh embodiment, [Gln¹]orexin A was identified as aphysiological substrate of QC within the present invention. Orexin A isa neuropeptide that plays a significant role in the regulation of foodintake and sleep-wakefulness, possibly by coordinating the complexbehavioral and physiologic responses of these complementary homeostaticfunctions. It plays also a role in the homeostatic regulation of energymetabolism, autonomic function, hormonal balance and the regulation ofbody fluids.

In a twelfth embodiment, the present invention provides the use ofeffectors of QC for the preparation of a medicament for the treatment ofimpaired food intake and sleep-wakefulness, impaired homeostaticregulation of energy metabolism, impaired autonomic function, impairedhormonal balance and impaired regulation of body fluids.

Polyglutamine expansions in several proteins lead to neurodegenerativedisorders, such as Parkinson disease and Kennedy's disease. Themechanism therefore remains largely unknown. The biochemical propertiesof polyglutamine repeats suggest one possible explanation: endolyticcleavage at a glutaminyl-glutaminyl bond followed by pyroglutamateformation may contribute to the pathogenesis through augmenting thecatabolic stability, hydrophobicity, amyloidogenicity, and neurotoxicityof the polyglutaminyl proteins (Saido, T; Med Hypotheses (2000) March;54(3):427-9). In a thirteenth embodiment, the present invention providestherefore the use of effectors of QC for the preparation of a medicamentfor the treatment of Parkinson disease and Huntington's disease.

In a fourteenth embodiment, the present invention provides a general wayto reduce or inhibit the enzymatic activity of QC. Examples ofinhibitory compounds are also provided.

Inhibition of a mammalian QC was only detected initially for1,10-phenanthroline and reduced 6-methylpterin (Busby, W. H. J. et al.1987 J Biol Chem 262, 8532-8536). EDTA did not inhibit QC, thus it wasconcluded that QC is not a metal-dependent enzyme (Busby, W. H. J. etal. 1987 J Biol Chem 262, 8532-8536, Bateman, R. C. J. et al. 2001Biochemistry 40, 11246-11250, Booth, R. E. et al. 2004 BMC Biology 2).In the present invention, however, it is shown that human QC and otheranimal QCs are metal-dependent enzymes, as revealed by the inhibitioncharacteristics of QC by 1,10-phenanthroline, dipicolinic acid,8-hydroxy-quinoline and other chelators (FIGS. 18, 19) and by thereactivation of QC by transition metal ions (FIG. 20). Finally, themetal dependence is outlined by a sequence comparison to othermetal-dependent enzymes, showing a conservation of the chelating aminoacid residues also in human QC (FIG. 21). The interaction of compoundswith the active-site bound metal ion represents a general way to reduceor inhibit QC activity.

In the present invention it is shown that imidazole derivatives arepotent inhibitors of QC. Using the continuous assay (for details seeexample 2), many imidazole derivatives were analyzed concerning theirability to inhibit the human QC as a member of the highly conservedmammalian QCs.

Thus, the present invention provides imidazole derivatives and histidineand its derivatives as activity reducing effectors of QC and theircharacteristics in terms of inhibition type and potency. Structures andK_(i)-values are shown in tables 3 and 4. The results are described indetail in example 7.

TABLE 3 Inhibitory constants of imidazole derivatives in the human QCcatalyzed reaction. Determinations were performed at 30° C. in 0.05 MTris-HCL pH 8.0, containing 5 mM EDTA. Compound K_(i)-value (mM)Structure core structures imidazole 0.103 ± 0.004 benzimidazole 0.138 ±0.005 N-1 derivatives 1-benzylimidazole 0.0071 ± 0.00031-methylimidazole 0.030 ± 0.001 1-vinylimidazole 0.049 ± 0.002 oxalicacid diimidazolidide 0.078 ± 0.002 N-acetylimidazole 0.107 ± 0.003N-(trimethylsilyl)-imidazole 0.167 ± 0.007 N-benzoylimidazole 0.174 ±0.007 1-(2-oxo-2-phenyl-ethyl)- 0.184 ± 0.005 imidazole1-(3-aminopropyl)-imidazole 0.41 ± 0.01 1-phenylimidazole no inhibition1,1′-sulfonyldiimidazole no inhibition C-4(5) derivativesN-omega-acetylhistamine 0.017 ± 0.001 L-histidinamide 0.56 ± 0.04H-His-Trp-OH 0.60 ± 0.03 L-histidinol 1.53 ± 0.12 L-histidine 4.4 ± 0.24-imidazole-carboxaldehyde 7.6 ± 0.7 imidazole-4-carbonic acid 14.5 ±0.6  methylester L-histamine 0.85 ± 0.04 C-4,5 derivatives5-hydroxymethyl-4-methyl- 0.129 ± 0.005 imidazole4-amino-imidazole-5-carbonic 15.5 ± 0.5  acid amide4,5-diphenyl-imidazole no inhibition 4,5-dicyanoimidazole no inhibitionC-2 derivatives 2-methyl-benzylimidazole 0.165 ± 0.0042-ethyl-4-methyl-imidazole 0.58 ± 0.04 2-aminobenzimidazole 1.8 ± 0.12-chloro-1H-benzimidazole no inhibition Others3-(1H-imidazol-1-yl)-1-(3-methylbenzo[b]thiophene-2-yl)propan-1-one0.0025 ± 0.0001

4-[(1-methyl-1H-imidazol-5-yl)methyl]-3-propyldihydrofuran-2-(3H)-one0.0067 ± 0.0003

4-[2-(1H-imidazol-1-yl)-ethoxy]benzoic acid 0.0034 ± 0.0001

3-[3-(1H-imidazol-1-yl)propyl]-2-thioxoimidazolidin-4-one 0.00041 ±0.00001

5-nitro-2-[2-([{3-(1H-imidazol-1-yl-)propyl}amino]carbonyl)phenyl]furamide0.0066 ± 0.0004

N-(4-chlorophenyl)-N′-[2-(1H-imidazol-1-yl)ethyl]thiourea 0.00165 ±0.00007

2-[(5-imidazol-1-ylmethyl-pyrrolidine-2-carbonyl)-amino]-propionic acidmethyl ester 0.0322 ± 0.0007

2-[(5-Imidazol-1-ylmethyl-2,3-dihydro-1H-pyrrole-2-carbonyl)-amino]-propionicacid methyl ester n.d

Imidazo<1.5a>pyridine 0.0356 ± 0.0005

Methyl(2S)-2-{[(2S)-2-amino-5-(1H-imidazol-1-ylamino)-5-oxopentanoyl[amino}-3-methylbutanoate0.164 ± 0.004

TABLE 4 QC inhibition by L-histamine and its two biological metabolites(also known as tele-methylhistamine). Compound K_(i) value (mM)Structure L-histamine 0.85 ± 0.04

3-methyl-4-(β-aminoethyl)-imidazole 0.120 ± 0.004

1-methyl-4-(β-aminoethyl)-imidazole n.i

Surprisingly, during characterization of the enzymatic activity it wasdiscovered that besides an N-terminal glutaminyl residue, N-terminalβ-homo-glutaminyl residues also fulfill properties as substrates of QCsfrom plants and mammals. The N-terminal β-homo-glutaminyl residue wasconverted into a five-membered lactam ring by catalysis of human andpapaya QC, respectively. The results are described in example 5. Theapplied method is illustrated in example 2 and the peptide synthesis wasperformed as described in example 6.

Another preferred embodiment of the present invention comprisesscreening methods for effectors of QC.

A preferred screening method for identifying activity modifyingeffectors of QC from a group of compounds comprises the steps of:

-   -   a) Contacting said compounds with QC under conditions which        would permit binding therebetween;    -   b) Adding a substrate of QC;    -   c) Monitoring the conversion of the substrate or optionally        measuring the residual QC activity; and    -   d) Calculating changes in the substrate conversion and/or enzyme        activity of QC to identify an activity modifying effector.

Another preferred screening method relates to a method for theidentification and selection of effectors which interact directly orindirectly with the active-site bound metal ion of QC and comprises thefollowing steps:

-   -   a) Contacting said compounds with QC under conditions which        would permit binding therebetween;    -   b) Adding a substrate of QC which is subject to conversion by        QC;    -   c) Monitoring the conversion of the substrate or optionally        measuring the residual QC activity; and    -   d) Calculating changes in the substrate conversion and/or enzyme        activity of QC wherein changes may be used to identify an        activity modifying effector of QC.

Preferred for the use in the above described screening methods aremammalian QC or Papaya QC. Especially preferred is mammalian QC, sincethe effectors identified by these screening methods shall be used forthe treatment of diseases in mammals, especially in humans.

The agents selected by the above described screening methods can work bydecreasing the conversion of at least one substrate of QC (negativeeffectors, inhibitors), or by increasing the conversion of at least onesubstrate of QC (positive effectors, activators).

The compounds of the present invention can be converted into acidaddition salts, especially pharmaceutically acceptable acid additionsalts.

The salts of the compounds of the invention may be in the form ofinorganic or organic salts.

The compounds of the present invention can be converted into and used asacid addition salts, especially pharmaceutically acceptable acidaddition salts. The pharmaceutically acceptable salt generally takes aform in which a basic side chain is protonated with an inorganic ororganic acid. Representative organic or inorganic acids includehydrochloric, hydrobromic, perchloric, sulfuric, nitric, phosphoric,acetic, propionic, glycolic, lactic, succinic, maleic, fumaric, malic,tartaric, citric, benzoic, mandelic, methanesulfonic,hydroxyethanesulfonic, benzenesulfonic, oxalic, pamoic,2-naphthalenesulfonic, p-toulenesulfonic, cyclohexanesulfamic,salicylic, saccharinic or trifluoroacetic acid. All pharmaceuticallyacceptable acid addition salt forms of the compounds of the presentinvention are intended to be embraced by the scope of this invention.

In view of the close relationship between the free compounds and thecompounds in the form of their salts, whenever a compound is referred toin this context, a corresponding salt is also intended, provided such ispossible or appropriate under the circumstances.

Where the compounds according to this invention have at least one chiralcenter, they may accordingly exist as enantiomers. Where the compoundspossess two or more chiral centers, they may additionally exist asdiastereomers. It is to be understood that all such isomers and mixturesthereof are encompassed within the scope of the present invention.Furthermore, some of the crystalline forms of the compounds may exist aspolymorphs and as such are intended to be included in the presentinvention. In addition, some of the compounds may form solvates withwater (i.e. hydrates) or common organic solvents, and such solvates arealso intended to be encompassed within the scope of this invention.

The compounds, including their salts, can also be obtained in the formof their hydrates, or include other solvents used for theircrystallization.

In a further embodiment, the present invention provides a method ofpreventing or treating a condition mediated by modulation of the QCenzyme activity in a subject in need thereof which comprisesadministering any of the compounds of the present invention orpharmaceutical compositions thereof in a quantity and dosing regimentherapeutically effective to treat the condition. Additionally, thepresent invention includes the use of the compounds of this invention,and their corresponding pharmaceutically acceptable acid addition saltforms, for the preparation of a medicament for the prevention ortreatment of a condition mediated by modulation of the QC activity in asubject. The compound may be administered to a patient by anyconventional route of administration, including, but not limited to,intravenous, oral, subcutaneous, intramuscular, intradermal, parenteraland combinations thereof.

In a further preferred form of implementation, the invention relates topharmaceutical compositions, that is to say, medicaments, that containat least one compound of the invention or salts thereof, optionally incombination with one or more pharmaceutically acceptable carriers and/orsolvents.

The pharmaceutical compositions may, for example, be in the form ofparenteral or enteral formulations and contain appropriate carriers, orthey may be in the form of oral formulations that may containappropriate carriers suitable for oral administration. Preferably, theyare in the form of oral formulations.

The effectors of QC activity administered according to the invention maybe employed in pharmaceutically administrable formulations orformulation complexes as inhibitors or in combination with inhibitors,substrates, pseudosubstrates, inhibitors of QC expression, bindingproteins or antibodies of those enzyme proteins that reduce the QCprotein concentration in mammals. The compounds of the invention make itpossible to adjust treatment individually to patients and diseases, itbeing possible, in particular, to avoid individual intolerances,allergies and side-effects.

The compounds also exhibit differing degrees of activity as a functionof time. The doctor providing treatment is thereby given the opportunityto respond differently to the individual situation of patients: he isable to adjust precisely, on the one hand, the speed of the onset ofaction and, on the other hand, the duration of action and especially theintensity of action.

A preferred treatment method according to the invention represents a newapproach for the prevention or treatment of a condition mediated bymodulation of the QC enzyme activity in mammals. It is advantageouslysimple, susceptible of commercial application and suitable for use,especially in the treatment of diseases that are based on unbalancedconcentration of physiological active QC substrates, e.g. listed inTables 1 and 2, in mammals and especially in human medicine.

The compounds may be advantageously administered, for example, in theform of pharmaceutical preparations that contain the active ingredientin combination with customary additives like diluents, excipients and/orcarriers known from the prior art. For example, they can be administeredparenterally (for example i.v. in physiological saline solution) orenterally (for example orally, formulated with customary carriers).

Depending upon their endogenous stability and their bioavailability, oneor more doses of the compounds can be given per day in order to achievethe desired normalisation of the blood glucose values. For example, sucha dosage range in humans may be in the range of from about 0.01 mg to250.0 mg per day, preferably in the range of from about 0.01 to 100 mgof compound per kilogram of body weight.

By administering effectors of QC activity to a mammal it could bepossible to prevent or alleviate or treat conditions selected fromAlzheimer's disease, Down Syndrome, ulcer disease and gastric cancerwith or w/o Heliobacter pylori infections, pathogenic psychoticconditions, schizophrenia, infertility, neoplasia, inflammatory hostresponses, cancer, psoriasis, rheumatoid arthritis, atherosclerosis,impaired humoral and cell-mediated immune responses, leukocyte adhesionand migration processes in the endothelium, impaired food intake,sleep-wakefulness, impaired homeostatic regulation of energy metabolism,impaired autonomic function, impaired hormonal balance and impairedregulation of body fluids.

Further, by administering effectors of QC activity to a mammal it couldbe possible to stimulate gastrointestinal tract cell proliferation,preferably proliferation of gastric mucosal cells, epithelial cells,acute acid secretion and the differentiation of acid producing parietalcells and histamine-secreting enterochromaffin-like cells.

In addition, administration of QC inhibitors to mammals may lead to aloss of sperm cell function thus suppressing male fertility. Thus, thepresent invention provides a method for the regulation and control ofmale fertility and the use of activity lowering effectors of QC for thepreparation of contraceptive medicaments for males.

Furthermore, by administering effectors of QC activity to a mammal itmay be possible to suppress the proliferation of myeloid progenitorcells.

The compounds used according to the invention can accordingly beconverted in a manner known per se into conventional formulations, suchas, for example, tablets, capsules, dragées, pills, suppositories,granules, aerosols, syrups, liquid, solid and cream-like emulsions andsuspensions and solutions, using inert, non-toxic, pharmaceuticallysuitable carriers and additives or solvents. In each of thoseformulations, the therapeutically effective compounds are preferablypresent in a concentration of approximately from 0.1 to 80% by weight,more preferably from 1 to 50% by weight, of the total mixture, that isto say, in amounts sufficient for the mentioned dosage latitude to beobtained.

The substances can be used as medicaments in the form of dragées,capsules, bitable capsules, tablets, drops, syrups or also assuppositories or as nasal sprays.

The formulations may be advantageously prepared, for example, byextending the active ingredient with solvents and/or carriers,optionally with the use of emulsifiers and/or dispersants, it beingpossible, for example, in the case where water is used as diluent, fororganic solvents to be optionally used as auxiliary solvents.

Examples of excipients useful in connection with the present inventioninclude: water, non-toxic organic solvents, such as paraffins (forexample natural oil fractions), vegetable oils (for example rapeseedoil, groundnut oil, sesame oil), alcohols (for example ethyl alcohol,glycerol), glycols (for example propylene glycol, polyethylene glycol);solid carriers, such as, for example, natural powdered minerals (forexample highly disperse silica, silicates), sugars (for example rawsugar, lactose and dextrose); emulsifiers, such as non-ionic and anionicemulsifiers (for example polyoxyethylene fatty acid esters,polyoxyethylene fatty alcohol ethers, alkylsulphonates andarylsulphonates), dispersants (for example lignin, sulphite liquors,methylcellulose, starch and polyvinylpyrrolidone) and lubricants (forexample magnesium stearate, talcum, stearic acid and sodium laurylsulphate) and optionally flavourings.

Administration may be carried out in the usual manner, preferablyenterally or parenterally, especially orally. In the case of enteraladministration, tablets may contain in addition to the mentionedcarriers further additives such as sodium citrate, calcium carbonate andcalcium phosphate, together with various additives, such as starch,preferably potato starch, gelatin and the like. Furthermore, lubricants,such as magnesium stearate, sodium lauryl sulphate and talcum, can beused concomitantly for tabletting. In the case of aqueous suspensionsand/or elixirs intended for oral administration, various tastecorrectives or colourings can be added to the active ingredients inaddition to the above-mentioned excipients.

In the case of parenteral administration, solutions of the activeingredients using suitable liquid carriers can be employed. In general,it has been found advantageous to administer, in the case of intravenousadministration, amounts of approximately from 0.01 to 2.0 mg/kg,preferably approximately from 0.01 to 1.0 mg/kg, of body weight per dayto obtain effective results and, in the case of enteral administration,the dosage is approximately from 0.01 to 2 mg/kg, preferablyapproximately from 0.01 to 1 mg/kg, of body weight per day.

It may nevertheless be necessary in some cases to deviate from thestated amounts, depending upon the body weight of the experimentalanimal or the patient or upon the type of administration route, but alsoon the basis of the species of animal and its individual response to themedicament or the interval at which administration is carried out.Accordingly, it may be sufficient in some cases to use less than theabove-mentioned minimum amount, while, in other cases, the mentionedupper limit will have to be exceeded. In cases where relatively largeamounts are being administered, it may be advisable to divide thoseamounts into several single doses over the day. For administration inhuman medicine, the same dosage latitude is provided. The above remarksapply analogously in that case.

EXAMPLES OF PHARMACEUTICAL FORMULATIONS

1. Capsules Containing 100 mg of a Compound of the Invention perCapsule:

For approximately 10,000 capsules a solution of the followingcomposition is prepared:

compound of the invention 1.0 kg glycerol 0.5 kg polyethylene glycol 3.0kg water 0.5 kg 5.0 kg

The solution is introduced into soft gelatin capsules in a manner knownper se. The capsules are suitable for chewing or swallowing.

2. Tablets or Coated Tables or Dragées Containing 100 mg of a Compoundof the Invention:

The following amounts refer to the preparation of 100,000 tablets:

compound of the invention, 10.0 kg finely ground glucose 4.35 kg lactose4.35 kg starch 4.50 kg cellulose, finely ground 4.50 kg

The above constituents are mixed and then provided with a solutionprepared from

polyvinylpyrrolidone 2.0 kg polysorbate 0.1 kg and water approx. 5.0 kgand granulated in a manner known per se by grating the moist mass and,after the addition of 0.2 kg of magnesium stearate, drying it. Thefinished tablet mixture of 30.0 kg is processed to form convex tabletsweighing 300 mg. Ideally, the tablets can be coated or sugar-coated in amanner known per se.

The pharmaceutical compositions defined throughout the specificationadvantageously contain a combination of at least one effector of QCactivity and at least one DP IV inhibitor. Such pharmaceuticalcompositions are especially useful for the treatment of Alzheimer'sDisease and Down Syndrome.

Example 1 Preparation of Human and Papaya QC

Host Strains and Media

Pichia pastoris strain X33 (AOX1, AOX2), used for the expression ofhuman QC was grown, transformed and analyzed according to themanufacturer's instructions (Invitrogen). The media required for P.pastoris, i.e. buffered glycerol (BMGY) complex or methanol (BMMY)complex medium, and the fermentation basal salts medium were preparedaccording to the manufacturer's recommendations.

Molecular Cloning of Plasmid Vectors Encoding the Human QC

All cloning procedures were done applying standard molecular biologytechniques. For expression in yeast, the vector pPICZαB (Invitrogen) wasused. The pQE-31 vector (Qiagen) was used to express the human QC in E.coli. The cDNA of the mature QC starting with codon 38 was fused inframe with the plasmid encoded 6×histidine tag. After amplificationutilizing the primers pQCyc-1 and pQCyc-2 (Table 1) and subcloning, thefragment was inserted into the expression vector employing therestriction sites of SphI and HindIII.

Transformation of P. pastoris and Mini-Scale Expression

Plasmid DNA was amplified in E. coli JM109 and purified according to therecommendations of the manufacturer (Qiagen). In the expression plasmidused, pPICZαB, three restriction sites are provided for linearization.Since SacI and BstXI cut within the QC cDNA, PmeI was chosen forlinearization. 20-30 μg plasmid DNA was linearized with PmeI,precipitated by ethanol, and dissolved in sterile, deionized water. 10μg of the DNA was then applied for transformation of competent P.pastoris cells by electroporation according to the manufacturer'sinstructions (BioRad). Selection was done on plates containing 150 μg/mlZeocin. One transformation using the linearized plasmid yielded severalhundred transformants.

In order to test the recombinant yeast clones for QC expression,recombinants were grown for 24 h in 10 ml conical tubes containing 2 mlBMGY. Afterwards, the yeast was centrifuged and resuspended in 2 ml BMMYcontaining 0.5% methanol. This concentration was maintained by additionof methanol every 24 h up to 72 h. Subsequently, QC activity in thesupernatant was determined. The presence of the fusion protein wasconfirmed by western blot analysis using an antibody directed againstthe 6×histidine tag (Qiagen). Clones that displayed the highest QCactivity were chosen for further experiments and fermentation.

Large-Scale Expression in a Fermenter

Expression of the QC was performed in a 5 l reactor (Biostat B, B. Braunbiotech), essentially as described in the “Pichia fermentation processguidelines” (Invitrogen). Briefly, the cells were grown in thefermentation basal salts medium supplemented with trace salts, and withglycerol as the sole carbon source (pH 5.5). During an initial batchphase for about 24 h and a subsequent fed-batch phase for about 5 h,cell mass was accumulated. Once a cell wet weight of 200 g/l wasachieved, induction of QC expression was performed using methanolapplying a three-step feeding profile for an entire fermentation time ofapproximately 60 h. Subsequently, cells were removed from theQC-containing supernatant by centrifugation at 6000×g, 40° C. for 15min. The pH was adjusted to 6.8 by addition of NaOH, and the resultantturbid solution was centrifuged again at 37000×g, 4° C. for 40 min. Incases of continued turbidity, an additional filtration step was appliedusing a cellulose membrane (pore width 0.45 μm).

Purification of 6× Histidine Tagged QC Expressed in P. pastoris

The His-tagged QC was first purified by immobilized metal affinitychromatography (IMAC). In a typical purification, 1000 ml of culturesupernatant were applied to a Ni²⁺-loaded Chelating Sepharose FF column(1.6×20 cm, Pharmacia), that was equilibrated with 50 mM phosphatebuffer, pH 6.8, containing 750 mM NaCl, at a flow rate of 5 ml/min.After washing with 10 column volumes of equilibration buffer and 5column volumes of equilibration buffer containing 5 mM histidine, thebound protein was eluted by a shift to 50 mM phosphate buffer, pH 6.8,containing 150 mM NaCl and 100 mM histidine. The resulting eluate wasdialyzed against 20 mM Bis-Tris/HCl, pH 6.8, at 4° C. overnight.Subsequently, the QC was further purified by anion exchangechromatography on a Mono Q6 column (BioRad), equilibrated with dialysisbuffer. The QC-containing fraction was loaded onto the column using aflow rate of 4 ml/min. The column was then washed with equilibrationbuffer containing 100 mM NaCl. The elution was performed by twogradients resulting in equilibration buffer containing 240 mM and 360 mMNaCl in 30 or 5 column volumes, respectively. Fractions of 6 ml werecollected and the purity was analyzed by SDS-PAGE. Fractions containinghomogenous QC were pooled and concentrated by ultrafiltration. Forlong-term storage (−20° C.), glycerol was added to a final concentrationof 50%. Protein was quantified according to the methods of Bradford orGill and von Hippel (Bradford, M. M. 1976 Anal Biochem 72, 248-254;Gill, S. C. and von Hippel, P. H. 1989 Anal Biochem 182, 319-326.).

Expression and Purification of QC in E. coli

The construct encoding the QC was transformed into M15 cells (Qiagen)and grown on selective LB agar plates at 37° C. Protein expression wascarried out in LB medium containing 1% glucose and 1% ethanol at roomtemperature. When the culture reached an OD₆₀₀ of approximately 0.8,expression was induced with 0.1 mM IPTG overnight. After one cycle offreezing and thawing, cells were lysed at 4° C. by addition of 2.5 mg/mllysozyme in 50 mM phosphate buffer, pH 8.0, containing 300 mM NaCl and 2mM histidine for approximately 30 min. The solution was clarified bycentrifugation at 37000×g, 4° C. for 30 min, followed by a filtrationapplying a glass frit (DNA separation) and two additional filtrationsteps applying cellulose filters for crude and fine precipitates. Thesupernatant (approx. 500 ml) was applied onto a Ni²⁺-affinity column(1.6×20 cm) at a flow rate of 1 ml/min. Elution of QC was carried outwith 50 mM phosphate buffer containing 150 mM NaCl and 100 mM histidine.The QC-containing fraction was concentrated by ultrafiltration.

Purification of QC from Papaya Latex

QC from papaya latex was prepared using the BioCAD 700E (PerseptiveBiosystems, Wiesbaden, Germany) with a modified version of a previouslyreported method (Zerhouni, S. et al. 1989 Biochim Biophys Acta 138,275-290). 50 g latex was dissolved in water and centrifugated asdescribed therein. Inactivation of proteases was performed with S-methylmethanethiosulfonate, and the resultant crude extract was dialyzed.After dialysis, the entire supernatant was loaded onto a (21×2.5 cmi.d.) SP Sepharose Fast Flow column, equilibrated with 100 mM sodiumacetate buffer, pH 5.0 (flow rate 3 ml/min). Elution was performed inthree steps by increasing sodium acetate buffer concentration at a flowrate of 2 ml/min. The first step was a linear gradient from 0.1 to 0.5 Macetate buffer in 0.5 column volumes. The second step was a linearincrease in buffer concentration from 0.5 to 0.68 M in four columnvolumes. During the last elution step, one column volume of 0.85 Mbuffer was applied. Fractions (6 ml) containing the highest enzymaticactivity were pooled. Concentration and buffer changes to 0.02 MTris/HCl, pH 8.0 were performed via ultrafiltration (Amicon; molecularmass cut-off of the membrane 10 kDa).

Ammonium sulfate was added to the concentrated papaya enzyme, obtainedfrom the ion exchange chromatography step to a final concentration of 2M. This solution was applied onto a (21×2.5 cm i.d.) Butyl Sepharose 4Fast Flow column (flow rate 1.3 ml/min), equilibrated with 2 M ammoniumsulfate, 0.02 M Tris/HCl, pH 8.0. Elution was performed in three stepswith decreasing concentrations of ammonium sulfate. During the firststep a linear gradient from 2 to 0.6 M ammonium sulfate, 0.02 MTris/HCl, pH 8.0 was applied for 0.5 column volumes at a flow rate of1.3 ml/min. The second step was a linear gradient from 0.6 to 0 Mammonium sulfate, 0.02 M Tris/HCl, pH 8.0, in 5 column volumes at a flowrate of 1.5 ml/min. The last elution step was carried out by applying0.02 M Tris/HCl at pH 8.0 for 2 column volumes at a flow rate of 1.5ml/min. All fractions containing QC activity were pooled andconcentrated by ultrafiltration. The resultant homogenous QC was storedat −70° C. Final protein concentrations were determined using the methodof Bradford, compared to a standard curve obtained with bovine serumalbumin.

Example 2 Assays for Glutaminyl Cyclase Activity

Fluorometric Assays

All measurements were performed with a BioAssay Reader HTS-7000Plus formicroplates (Perkin Elmer) at 30° C. QC activity was evaluatedfluorometrically using H-Gln-βNA. The samples consisted of 0.2 mMfluorogenic substrate, 0.25 U pyroglutamyl aminopeptidase (Unizyme,Hørsholm, Denmark) in 0.2 M Tris/HCl, pH 8.0 containing 20 mM EDTA andan appropriately diluted aliquot of QC in a final volume of 250 μl.Excitation/emission wavelengths were 320/410 nm. The assay reactionswere initiated by addition of glutaminyl cyclase. QC activity wasdetermined from a standard curve of β-naphthylamine under assayconditions. One unit is defined as the amount of QC catalyzing theformation of 1 μmolpGlu-βNA from H-Gln-βNA per minute under thedescribed conditions.

In a second fluorometric assay, QC was activity was determined usingH-Gln-AMC as substrate. Reactions were carried out at 30° C. utilizingthe NOVOStar reader for microplates (BMG labtechnologies). The samplesconsisted of varying concentrations of the fluorogenic substrate, 0.1 Upyroglutamyl aminopeptidase (Qiagen) in 0.05 M Tris/HCl, pH 8.0containing 5 mM EDTA and an appropriately diluted aliquot of QC in afinal volume of 250 μl. Excitation/emission wavelengths were 380/460 nm.The assay reactions were initiated by addition of glutaminyl cyclase. QCactivity was determined from a standard curve of7-amino-4-methylcoumarin under assay conditions. The kinetic data wereevaluated using GraFit software.

Spectrophotometric Assay of QC

This novel assay was used to determine the kinetic parameters for mostof the QC substrates. QC activity was analyzed spectrophotometricallyusing a continuous method, that was derived by adapting a previousdiscontinuous assay (Bateman, R. C. J. 1989 J Neurosci Methods 30,23-28) utilizing glutamate dehydrogenase as auxiliary enzyme. Samplesconsisted of the respective QC substrate, 0.3 mM NADH, 14 mMα-Ketoglutaric acid and 30 U/ml glutamate dehydrogenase in a finalvolume of 250 μl. Reactions were started by addition of QC and persuedby monitoring of the decrease in absorbance at 340 nm for 8-15 min.Typical time courses of product formation are presented in FIG. 1.

The initial velocities were evaluated and the enzymatic activity wasdetermined from a standard curve of ammonia under assay conditions. Allsamples were measured at 30° C., using either the SPECTRAFluor Plus orthe Sunrise (both from TECAN) reader for microplates. Kinetic data wasevaluated using GraFit software.

Inhibitor Assay

For inhibitor testing, the sample composition was the same as describedabove, except of the putative inhibitory compound added. For a rapidtest of QC-inhibition, samples contained 4 mM of the respectiveinhibitor and a substrate concentration at 1 K_(M). For detailedinvestigations of the inhibition and determination of K_(i)-values,influence of the inhibitor on the auxiliary enzymes was investigatedfirst. In every case, there was no influence on either enzyme detected,thus enabling the reliable determination of the QC inhibition. Theinhibitory constant was evaluated by fitting the set of progress curvesto the general equation for competitive inhibition using GraFitsoftware.

Example 3 MALDI-TOF Mass Spectrometry

Matrix-assisted laser desorption/ionization mass spectrometry wascarried out using the Hewlett-Packard G2025 LD-TOF System with a lineartime of flight analyzer. The instrument was equipped with a 337 nmnitrogen laser, a potential acceleration source (5 kV) and a 1.0 mflight tube. Detector operation was in the positive-ion mode and signalswere recorded and filtered using LeCroy 9350M digital storageoscilloscope linked to a personal computer. Samples (5 μl) were mixedwith equal volumes of the matrix solution. For matrix solution we usedDHAP/DAHC, prepared by solving 30 mg 2′,6′-dihydroxyacetophenone(Aldrich) and 44 mg diammonium hydrogen citrate (Fluka) in 1 mlacetonitrile/0.1% TFA in water (1/1, v/v). A small volume (=1 μl) of thematrix-analyte-mixture was transferred to a probe tip and immediatelyevaporated in a vacuum chamber (Hewlett-Packard G2024A sample prepaccessory) to ensure rapid and homogeneous sample crystallization.

For long-term testing of Glu¹-cyclization, Aβ-derived peptides wereincubated in 100 μl 0.1 M sodium acetate buffer, pH 5.2 or 0.1 MBis-Tris buffer, pH 6.5 at 30° C. Peptides were applied in 0.5 mM[Aβ3-11a] or 0.15 mM [Aβ3-21a] concentrations, and 0.2 U QC was addedall 24 hours.

In case of Aβ3-21a, the assays contained 1% DMSO. At different times,samples were removed from the assay tube, peptides extracted usingZipTips (Millipore) according to the manufacturer's recommendations,mixed with matrix solution (1:1 v/v) and subsequently the mass spectrarecorded. Negative controls did either contain no QC or heat deactivatedenzyme. For the inhibitor studies the sample composition was the same asdescribed above, with exception of the inhibitory compound added (5 mMbenzimidazole or 2 mM 1,10-phenanthroline).

Example 4 pH Dependence

The pH-dependence of catalysis of human and papaya QC was investigatedunder first-order rate conditions, thus reflecting the impact of theproton concentration on the specificity constant k_(cat)/K_(M). For thispurpose, the coupled enzymatic assay using pyroglutamyl aminopeptidaseas auxiliary enzyme and Gln-βNA as substrate was used. Pyroglutamylaminopeptidase was shown to be active and stable between pH 5.5-8.5(Tsuru, D. et al. 1978 J Biochem (Tokyo) 84, 467-476). Hence, the assayenabled the study of QC catalysis in this pH-region. The rate profilesobtained were fit to classical bell shaped curves, as shown in FIG. 2.The human QC bears a very narrow pH-dependence with an optimum at aboutpH 7.8-8.0. The rate tended to decrease at more basic pH. This is incontrast to the rate profile observed with papaya QC, which showed nodrop in activity up to pH 8.5 (FIG. 2, inset). However, both enzymes hadtheir optimum of specificity at pH 8. Surprisingly, evaluation of thecurves revealed identical pK_(a)-values in the acidic range of 7.17±0.02and 7.15±0.02 for human and papaya QC, respectively.

The reduction of the activity of human QC at basic pH-values wasobviously due to dissociation of a group with a pK_(a) of approximately8.5. In case of papaya QC, there was no excessive data point collectionin the basic pH-range possible to enable a reliable determination of thesecond pK_(a) value. This is supported by fitting of the data to asingle dissociation model, resulting in an almost identical pK_(a)-value(pK_(a) 7.13±0.03) compared to fitting the data to a double dissociationmodel. This indicates that both pK_(a)-values are fairly separated.

pH Stability

The stability of the glutaminyl cyclases was investigated by incubatingthe plant and animal enzymes at 30° C. for 30 min at different pH valuesbetween pH 4-10. Afterwards, QC activity was determined under standardconditions. The results are shown in FIG. 3.

The QC from papaya latex was stable in the pH-range studied, without anobvious trend for instability in the acidic or basic range. In contrast,human QC only showed a comparable stability in the pH-range between 7and 8.5, exhibiting a remarkable instability at pH values above pH 8.5and below pH 6. Thus, the region around pH 8 seems to be optimal foractivity and stability of plant and human QC and a suitable pH-value forperforming a substrate specificity comparison of the QCs.

Example 5 Determination of Substrate Specificity of QC

Spectrophotometric Assay

The continuous spectrophotometric assay was performed as described inexample 2. Accordingly, QC activity is reflected by a decrease inabsorbance at 340 nm caused by the ammonia release and subsequentconsumption of NADH/H⁺ due to formation of glutamate from α-ketoglutaricacid. As shown in FIG. 1, linear progress curves were monitored andthere was a linear relationship between the measured activity and theconcentration of QC. Furthermore, the kinetic parameters obtained forH-Gln-Gln-OH using the continuous assay presented here (Table 1) were ingood agreement with those obtained using the discontinuous method(K_(M)=175±18 μM, k_(cat)=21.3±0.6 s⁻¹). In addition, the kineticparameters for conversion of the substrates H-Gln-Ala-OH, H-Gln-Glu-OH,H-Gln-Gln-OH, H-Gln-OtBu and H-Gln-NH₂ by papaya QC shown in Table 1correspond well to those determined using a direct method at pH 8.8 and37° C. (Gololobov, M. Y. et al. 1996 Biol Chem Hoppe Seyler 377,395-398). Hence, it is quite obvious that the novel continuous assayprovides reliable results.

Di-, Tri- and Dipeptide-Surrogates

Utilizing the novel continuous assay described above, about 30 compoundswere tested as potential substrates of QC from C. papaya and human. Theresults are displayed in Table 5. By comparison of the specificities itwas shown, that nearly all of the short peptide substrates are moreefficiently converted by papaya QC compared to the human enzyme.Interestingly, for both enzymes substrates with large hydrophobicresidues in the second position are the most potent ones, as shown bythe specificities of H-Gln-Tyr-Ala-OH, H-Gln-Phe-Ala-NH₂ andH-Gln-Trp-Ala-NH₂ compared to those of other tripeptides or by thereactivities of the chromophoric substrates H-Gln-AMC, H-Gln-βNA andH-Gln-Tyr-OH in comparison to dipeptide substrates. For papaya QC, thisfinding is in agreement with earlier results showing that thespecificity is in correlation with the size of the second amino acidresidue (Gololobov, M. Y. et al. 1996 Biol Chem Hoppe Seyler 377,395-398). The only striking difference in specificity of the plant andanimal QC was observed in case of H-Gln-OtBu . Whereas the ester wasconverted by papaya QC with similar specificity compared to dipeptidesubstrates, it was converted about one order of magnitude slower byhuman QC.

Oligopeptides

Besides several dipeptides and tripeptides, a number of oligopeptideswas tested upon conversion by papaya and human QC (Table 5).Interestingly, the overall difference in the specificities between humanand plant QC for a set of tetrapeptides was not that large as it wasobserved for dipeptide and tripeptide substrates. This indicates thatthe amino acids in the 3^(rd) and 4^(th) position still affect thekinetic behavior especially of human QC. An exception, however, comprisethe peptides with a proline residue in the second amino acid positionwhich show noticeably reduced k_(cat)/K_(M) values in a set oftetrapeptides of the structure H-Gln-X_(aa)-Tyr-Phe-NH₂ (Table 5). Thereduction in specificity was more pronounced for human QC, leading to anapproximately 8-fold difference in the k_(cat)/K_(M)-value as comparedto papaya QC.

Slightly reduced specificities of human QC were also observed forconversion of substrates with a positively charged amino acid C-terminalof glutamine, as indicated by the specificities forH-Gln-Arg-Tyr-Phe-NH₂ (SEQ ID NO: 14), H-Gln-Arg-Tyr-Phe-NH₂ (SEQ ID NO:14) and H-Gln-Lys-Arg-Leu-NH₂ (SEQ ID NO: 15) as compared to othertetrapeptides. Apparently, the reduced specificity was mainly due to asmaller turnover number. This effect was not the case for the plantenzyme.

TABLE 5 Kinetic evaluation of peptide substrates of human and Papaya QC(n.r., not reactive; n.i., no inhibition; n.d., not determined; *, forsubstrate inhibition) Human QC Papaya QC K_(M) k_(cat) K_(i)*k_(cat)/K_(M) K_(M) k_(cat) K_(i)* k_(cat)/K_(M) Substrate (μM) (s⁻¹)(mM) (mM⁻¹ s⁻¹) (μM) (s⁻¹) (mM) (mM⁻¹ s⁻¹) H-Gln-OH n.r. n.r. n.d. n.r.n.d. n.d. n.d. 0.23 ± 0.1  H-Gln-AMC 54 ± 2  5.3 ± 0.1 n.d. 98 ± 2  42 ±1  39.4 ± 0.4  n.d. 938 ± 13  H-Gln-□NA 70 ± 3  20.6 ± 0.5  1.21 ± 0.07294 ± 6  38 ± 3  51.4 ± 1.4  1.20 ± 0.08 1353 ± 70  H-Gln-OtBu 1235 ±74  6.7 ± 0.2 n.i. 5.4 ± 0.2 223 ± 9  49.4 ± 0.6  n.i. 222 ± 6 H-Gln-NH₂ 409 ± 40  12.8 ± 0.5  n.i. 31 ± 2  433 ± 13  44.8 ± 0.4  n.i.103 ± 2  H-Gln-Gly-OH 247 ± 10  13.2 ± 0.2  n.i. 53 ± 1  641 ± 20  45.8± 0.4  n.i. 71 ± 2  H-Gln-Ala-OH 232 ± 5  57.2 ± 0.4  n.i. 247 ± 4  158± 8  69.8 ± 1.0  n.i. 442 ± 16  H-Gln-Gln-OH 148 ± 5  20.7 ± 0.2  n.i.140 ± 2  44 ± 3  43.2 ± 0.7  n.i. 982 ± 51  H-Gln-Glu-OH 359 ± 10  24.7± 0.2  n.i. 58 ± 1  106 ± 5  50.3 ± 0.6  n.i. 475 ± 17  H-Gln-Val-OH 196± 5  17.2 ± 0.1  n.i. 88 ± 2  n.d. n.d. n.i. n.d. H-Gln-Tyr-OH 211 ± 5 94 ± 1  n.i. 446 ± 6  n.d. n.d. n.i. n.d. H-Gln-Glu-Tyr- 79 ± 2  45.1 ±0.4  n.i. 524 ± 8  103 ± 4  53.6 ± 0.7  n.i. 520 ± 13  NH₂H-Gln-Gly-Pro- 130 ± 5  25.3 ± 0.2  n.i. 195 ± 7  333 ± 15  41.7 ± 0.5 n.i. 125 ± 4  OH H-Gln-Tyr-Ala- 101 ± 4  125 ± 1  n.i. 930 ± 27  63 ± 3 104.0 ± 1.0  n.i. 1650 ± 63  OH H-Gln-Phe-Ala- 69 ± 3  109 ± 1  n.i.1811 ± 64  111 ± 5  132.1 ± 0.6  n.i. 1190 ± 48  NH₂ H-Gln-Trp-Ala- 50 ±2  47.0 ± 0.7  n.i. 940 ± 24  78 ± 5  151.8 ± 2.6  n.i. 1946 ± 91  NH₂H-Gln-Arg-Gly- 143 ± 4  33.5 ± 0.4  n.i. 234 ± 4  123 ± 10  49.2 ± 1.7 n.i. 400 ± 19  Ile-NH₂ (SEQ ID NO: 16) H-Gln-Asn-Gly- 172 ± 5  56.6 ±0.5  n.i. 329 ± 7  153 ± 9  51.4 ± 0.9  n.i. 336 ± 14  Ile-NH₂ (SEQ IDNO: 17) H-Gln-Ser-Tyr- 55 ± 3  52.8 ± 0.8  n.i. 960 ± 38  135 ± 6  64.9± 1.0  n.i. 481 ± 14  Phe-NH₂ (SEQ ID NO: 18) H-Gln-Arg-Tyr- 55 ± 2 29.6 ± 0.3  n.i. 538 ± 14  124 ± 6  48.9 ± 0.7  n.i. 394 ± 13  Phe-NH₂(SEQ ID NO: 14) H-Gln-Pro-Tyr- 1889 ± 152  31.7 ± 1.2  n.i. 17 ± 1  149± 14  18.8 ± 0.6  n.i. 126 ± 8  Phe-NH₂ (SEQ ID NO: 19) H-Gln-His-Tyr-68 ± 3  55.4 ± 0.7  n.i. 815 ± 26  92 ± 7  75.9 ± 1.4  n.i. 825 ± 48 Phe-NH₂ (SEQ ID NO: 20) H-Gln-Gln-Tyr- 41 ± 2  41.4 ± 0.4  n.i. 1010 ±40  45 ± 2  52.9 ± 0.7  n.i. 1176 ± 37  Phe-NH₂ (SEQ ID NO: 21)H-Gln-Glu-Tyr- 47 ± 4  46 ± 1  n.i. 979 ± 62  100 ± 4  54.6 ± 0.6  n.i.546 ± 16  Phe-NH₂ (SEQ ID NO: 22) H-Gln-Glu-Ala- 77 ± 4  46 ± 1  n.i.597 ± 18  102 ± 4  53.7 ± 0.6  n.i. 526 ± 15  Ala-NH₂ (SEQ ID NO: 23)H-Gln-Glu-Tyr- 69 ± 2  42.1 ± 0.4  n.i. 610 ± 12  113 ± 5  44.7 ± 0.5 n.i. 396 ± 13  Ala-NH₂ (SEQ ID NO: 24) H-Gln-Glu-Ala- 39 ± 3  39 ± 1 n.i. 1000 ± 51  81 ± 3  48.5 ± 0.45 n.i. 599 ± 17  Phe-NH₂ (SEQ ID NO:25) H-Gln-Glu-Asp- 55 ± 2  45.8 ± 0.5  n.i. 833 ± 21  107 ± 6  58.5 ±0.4  n.i. 547 ± 27  Leu-NH₂ (SEQ ID NO: 26) H-Gln-Lys-Arg- 54 ± 3  33.4± 0.5  n.i. 619 ± 25  118 ± 6  48.2 ± 0.8  n.i. 408 ± 14  Leu-NH₂ (SEQID NO: 15)

The results obtained with the tetrapeptides give also rise to anotherconclusion. As already pointed out, papaya QC showed a higherselectivity for dipeptides. For some of the tetrapeptides, however,higher specificity-constants were observed with human QC, as shown inFIG. 4 providing a plot of the data given in Table 5, for a set ofpeptides containing glutamate in the second amino acid position.Furthermore, as the chain length increases from di- to tetrapeptides,the selectivity of human QC increases, in contrast to the resultsobtained with papaya QC. Additionally, the highest selectivity of humanQC was recorded for the peptides containing bulky hydrophobic residuesin the 3^(rd) and 4^(th) amino acid position, which indicate hydrophobicinteractions with the enzyme. By comparison of the kinetic parametersfor the respective peptides, the changes seem to be mainly due to lowerK_(M)-values, the turnover numbers for conversion of the peptides werefound to be similar. Thus, the higher selectivity of human QC for longerpeptides is considered to be the result of tighter binding of the morehydrophobic substrates to the enzyme.

The differences between human and plant QC observed with peptidescontaining hydrophobic amino acids in the 3^(rd) and 4^(th) positionbecomes also evident by a comparison of the specificity constants of theenzymes towards H-Gln-Arg-Gly-Ile-NH₂ (SEQ ID NO: 16) andH-Gln-Arg-Tyr-Phe-NH₂ (SEQ ID NO: 14) or H-Gln-Gln-OH andH-Gln-Gln-Tyr-Phe-OH (SEQ ID NO: 21).

Human QC was also found to be more selective for homologous substratescontaining N-terminal Gln and an increasing number of C-terminal Alaresidues (Table 6). While the selectivity of human QC increased withsubstrate length, there was no such a trend with the papaya QC. Sincehuman QC was less specific for a peptide containing a Ser residue in thesequence, also the nature of the side chain seems to be of importance(table 6).

TABLE 6 Influence of substrate length on the activity of human andPapaya QC Human QC Papaya QC K_(M) k_(cat) k_(cat)/K_(M) K_(M) k_(cat)k_(cat)/K_(M) Substrate (μM) (s⁻¹) (mM⁻¹ s⁻¹) (μM) (s⁻¹) (mM⁻¹ s⁻¹)H-Gln-Ala-NH₂ 155 ± 9  40.1 ± 0.9  259 ± 9  212 ± 21  62.8 ± 3.0  296 ±15  H-Gln-Ala-Ala-NH₂ 87 ± 3  76.3 ± 0.7  877 ± 22  164 ± 6  83.2 ± 1.0 507 ± 12  H-Gln-Ala-Ala-Ala- 65 ± 3  60.5 ± 0.7  1174 ± 43  197 ± 8 74.6 ± 1.0  379 ± 10  Ala-NH₂ (SEQ ID NO: 27) H-Gln-Ala-Ala-Ser- 79 ± 6 55.3 ± 1.6  700 ± 33  216 ± 6  78.5 ± 1.0  363 ± 5  Ala-Ala-NH₂ (SEQ IDNO: 28)Influence of Ionic Strength on Catalysis

Another parameter that was investigated concerning its influence on thesubstrate specificity was ionic strength. For that purpose, the kineticparameters for cyclization of several substrates were determined inpresence and absence of 0.5 M KCl (Table 7). Surprisingly, theselectivity for substrates with uncharged backbone did not changesignificantly by addition of the salt in case of QC from papaya latexand human QC. The specificity constants of the human QC for H-Gln-Ala-OHand H-Gln-Glu-OH, however, decreased by addition of KCl. As indicated bythe individual kinetic parameters, this effect was due to an increasingK_(M) and an only slightly decreasing k_(cat)-value. In case of papayaQC, there was no effect on either parameter detected. The effect seemednot to be due to the negatively charged substrate as such, sinceunchanged parameters were found for the negatively charged peptideH-Gln-Glu-Asp-Leu-NH₂ (SEQ ID NO: 26). An interesting effect of the saltaddition was found for the positively charged substratesH-Gln-Arg-Gly-Leu-NH₂ (SEQ ID NO: 16) and H-Gln-Lys-Arg-Leu-NH₂ (SEQ IDNO: 15). In case of plant and human QC, a positive effect on catalysiswas determined mainly due to a smaller K_(M) value and a slightly higherturnover number.

TABLE 7 Influence of ionic strength on catalysis of human and Papaya QC0.05 M Tricine-NaOH, pH 8.08 0.05 M Tricine-NaOH, pH 8.0, 0.5 M KClK_(M) k_(cat) k_(cat)/K_(M) K_(i) K_(M) k_(cat) k_(cat)/K_(M) K_(i)Substrate (mM) (s⁻¹) (mM⁻¹ s⁻¹) (mM) (mM) (s⁻¹) (mM⁻¹ s⁻¹) (mM) PapayaH-Gln-NH₂ 0.434 ± 0.015 43.4 ± 0.4  100 ± 3  n.i. 0.446 ± 0.010 45.2 ±0.3  101 ± 2  n.i. QC H-Gln-βNA 0.036 ± 0.002 48.8 ± 1.0  1356 ± 50 1.14 ± 0.05 0.032 ± 0.002 47.2 ± 0.8  1475 ± 70  1.33 ± 0.07H-Gln-Ala-OH 0.137 ± 0.007 69.7 ± .9  509 ± 19  n.i. 0.143 ± 0.005 68.1± 0.6  480 ± 12  n.i. H-Gln-Glu-OH 0.098 ± 0.005 45.0 ± 0.5  459 ± 18 n.i. 0.094 ± 0.003 44.4 ± 0.3  472 ± 12  n.i. H-Gln-Trp-Ala-NH₂ 0.079 ±0.005 138 ± 3  1747 ± 73  n.i. 0.072 ± 0.004 133 ± 3  1847 ± 61  n.i.H-Gln-Arg-Gly- 0.106 ± 0.008 52.9 ± 1.2  499 ± 26  n.i. 0.065 ± 0.00548.4 ± 1.0  745 ± 42  n.i. Ile-NH₂ (SEQ ID NO: 16) H-Gln-Lys-Arg- 0.102± 0.007 50 ± 1  493 ± 22  n.i. 0.053 ± 0.002 58.1 ± 0.7  1096 ± 28  n.i.Leu-NH₂ (SEQ ID NO: 15) H-Gln-Glu-Asp- 0.109 ± 0.005 52.4 ± 0.7  481 ±16  n.i. 0.094 ± 0.003 53.6 ± 0.5  570 ± 13  n.i. Leu-NH₂ (SEQ ID NO:26) 0.05 M Tris-HCl, pH 8.0, 0.5 M 0.05 M Tris-HCl, pH 8.0 KCl HumanH-Gln-NH₂ 0.442 ± 0.030 12.8 ± 0.3  29 ± 1  n.i. 0.401 ± 0.014 12.2 ±0.1  30 ± 1  n.i. QC H-Gln-βNA 0.076 ± 0.004 21.7 ± 0.5  285 ± 8  1.39 ±0.08 0.063 ± 0.003 20.0 ± 0.4  318 ± 9  0.97 ± 0.04 H-Gln-Ala-OH 0.269 ±0.007 54.4 ± 0.5  202 ± 3  n.i. 0.357 ± 0.012 47.6 ± 0.6  133 ± 3  n.i.H-Gln-Glu-OH 0.373 ± 0.015 21.4 ± 0.3  57 ± 2  n.i. 0.607 ± 0.036 18.9 ±0.5  31 ± 1  n.i. H-Gln-Trp-Ala- 0.054 ± 0.003 50.8 ± 0.6  941 ± 41 n.i. 0.056 ± 0.002 50.0 ± 0.4  893 ± 25  n.i. NH₂ H-Gln-Arg-Gly- 0.166 ±0.013 31 ± 1  187 ± 9  n.i. 0.091 ± 0.005 29.8 ± 0.5  327 ± 12  n.i.Ile-NH₂ (SEQ ID NO: 16) H-Gln-Lys-Arg- 0.051 ± 0.003 29.4 ± 0.5  577 ±24  n.i. 0.034 ± 0.001 31.6 ± 0.3  929 ± 19  n.i. Leu-NH₂ (SEQ ID NO:15) H-Gln-Glu-Asp- 0.060 ± 0.002 46.6 ± 0.5  777 ± 18  n.i. 0.061 ±0.002 45.6 ± 0.5  748 ± 16  n.i. Leu-NH₂ (SEQ ID NO: 26)Physiological Substrates

In earlier studies, conversion of [Gln¹]-TRH and [Gln¹]-GnRH by QC wasalready shown for the QC from bovine and porcine pituitary (Busby, W. H.J. et al. 1987 J Biol Chem 262, 8532-8536; Fischer, W. H. and Spiess, J.1987 Proc Natl Acad Sci USA 84, 3628-3632). In addition to these alreadyinvestigated pituitary hormones, three potential physiologicalsubstrates of human QC were synthesized and tested upon conversion,namely [Gln¹]Gastrin, [Gln¹]Neurotensin, and [Gln¹]FPP. The kineticparameters for their conversion are listed in Table 1. Interestingly,the glutaminyl peptides are converted to the respective pyroglutamylpeptides with increasing specificity constants depending on their size,i.e., the first largest peptide pro-gastrin with 17 amino acids followedby pro-neurotensin, pro-GnRH, pro-TRH and pro-FPP. These findingscorrespond to the data obtained with the synthetic peptides.

Surprisingly, the longer substrates are also converted with higherselectivity by the plant enzyme, a result that contrasts in part withthe findings for the shorter oligopeptides. Possibly, there aresecondary binding interactions between substrate and enzyme far distantfrom the active site.

Peptides Comprising Modified Amino Acids

In order to further investigate the specificity and selectivity of theQCs, peptides were synthesized comprising either a modified N-terminalglutaminyl residue or a modified amino acid in the second position. Theconversion of these peptides was investigated qualitatively utilizingMALDI-TOF mass spectrometry (see also example 3). Due to the cyclizationof the glutaminyl residue or its analog, respectively, a mass differenceof the substrate and the product of catalysis is detected. In cases ofammonia liberation of one mole per mole of substrate, the conversion wasalso analyzed quantitatively using the spectrophotometric assay.

H-Gln-Lys(Gln)-Arg-Leu-Ala-NH₂. This N-terminally branched peptide,comprising two glutaminyl residues at the N-terminus that are bound to alysyl residue via a peptide- and partial isopeptide bond, was convertedby human (FIG. 5) and papaya QC (not shown) in an apparently identicalmanner. Both glutaminyl residues were converted into pyroglutamic acid,without any detectable preference for a distinct residue, as indicatedby the consistent substrate conversion (FIG. 5). Thus, the selectivityof the QCs for the differently bound glutaminyl residues differs notfundamentally.

H-Gln(NMe)-Phe-Lys-Ala-Glu-NH₂. (SEQ ID NO: 2). The methylatedglutaminyl residue was only converted into a pyroglutamyl residue bypapaya QC (FIG. 6). Additionally, an inhibition of the human QC by thepeptide was not detected, indicating that the methylated residue is notrecognized by human QC.

H-Glu(OMe)-βNA and H-Glu-βNA. Neither of these compounds were convertedby papaya or human QC. These fluorogenic substrates were analyzedfluorometrically, utilizing pyroglutamyl aminopeptidase as auxiliaryenzyme. The O-methylated glutamate residue, however, showed a remarkableinstability in both, Tris and Tricine buffers tending toanon-enzymatically catalyzed cyclization. Furthermore, activity of bothQCs against H-Gln-AMC as substrate was not inhibited by the longerpeptides H-Glu(OMe)-Phe-Lys-Arg-Leu-Ala-NH₂ (SEQ ID NO: 29) orH-Glu-Phe-Lys-Arg-Leu-Ala-NH₂, (SEQ ID NO: 30), indicating that glutamicacid or derivatives are not recognized by both QC forms. Furthermore,the result implies that not only the negative charge of the glutamicacid residue is the reason for the repulsion of the peptide from theactive site.

H-Gln-cyclo(Nε-Lys-Arg-Pro-Ala-Gly-Phe). The conversion ofH-Gln-cyclo(Nε-Lys-Arg-Pro-Ala-Gly-Phe), which contains anintramolecular partial isopeptide bond was analyzed quantitatively,revealing K_(M)-values of 240±14 μM and 133±5 μM for human and papayaQC, respectively. Due to the higher turnover number of conversion bypapaya QC (49.4±0.6 s⁻¹) compared to human QC (22.8±10.6 s⁻¹), the plantenzyme exhibits with 372±9 mM⁻¹ min⁻¹ an approximately 4-fold higherk_(cat)/K_(M)-value than the human QC. Thus, the specificity constant isin case of the papaya QC only slightly smaller compared to substrateshaving a similar size, such as H-Gln-Ala-Ala-Ser-Ala-Ala-NH₂. (SEQ IDNO: 28). The k_(cat)/K_(M)-value for human QC, however, was foundwith95±3 mM⁻¹ s⁻¹ to be approximately one order of magnitude smaller incomparison with substrates of similar size (Table 5).

H-βhomoGln-Phe-Lys-Arg-Leu-Ala-NH₂(SEQ ID NO: 31). The N-terminalβ-homoglutaminyl residue was converted into a five-membered lactam ringby catalysis of human and papaya QC, respectively. The concomitantliberation of ammonia was analyzed spectrophotometrically and byMALDI-tof analysis as described before. There was no liberation ofammonia detected when QC was omitted or boiled, indicating a specificcatalysis of the cyclization. Interestingly, the QC from C. papaya(K_(M)=3.1±0.3 mM, k_(cat)=4.0±0.4 s⁻¹) and human (K_(M)=2.5±0.2 mM,k_(cat)=3.5±0.1 s⁻¹) catalyze the conversion of this peptide with almostidentical k_(cat)/K_(M) values of 1.4±0.1 and 1.3±0.1 mM⁻¹s⁻¹,respectively. Thus, the cyclization of the β-homoglutamine residue iscatalyzed with an approximately 1000-fold reduced efficiency compared topeptides of similar size containing a glutaminyl residue at theirN-terminus. This shows that the constitution of the α-carbon of thesubstrate is important for substrate recognition by the QC forms, butnot essential. The essential requirement for being a substrate is aγ-amide group and an unprotonated N-terminal amino group in distance andangle prone for cyclization, a requirement that is fulfilled byN-terminalglutaminyl and β-homo-glutaminyl residues.

Example 6 Synthesis of the QC Substrates

Oligopeptides. Peptides were synthesized semiautomatically in 0.5 mmolscale using a peptide synthesizer (Labortec SP650, Bachem, Switzerland)as previously described (Schilling, S. et al. 2002 Biochemistry 41,10849-10857). Longer peptides were synthesized in 25 μmol scale usingthe automated Symphony peptide synthesizer (Rainin Instrument Co.) asdescribed (Manhart, S. et al. 2003 Biochemistry 42, 3081-3088). For allpeptide couplings modified Fmoc-protocols of solid-phase peptidesynthesis were employed using2-(1H-Benzotriazole-1-yl)-1,1,3,3,-tetramethyluronium tetrafluoroborate(TBTU; Novabiochem)/base (diisopropyl ethylamine or N-methyl-morpholine;Merck) or in case of difficult couplingsN-[(Dimethylamino)-1H-1,2,3,-triazolo[4,5-b]pyridin-1-ylmethylene]-N-methylmethanamminiumhexafluorophosphate N-oxide (4,5) (HATU; Applied Biosystems)/diisopropylethylamine as activating reagents were used. After cleavage from theresin by trifluoroacetic acid (TFA; Merck) containing cocktail, thecrude peptides were purified by preparative HPLC with acid free solventsin order to avoid further cyclization of the N-terminal glutamine.Preparative HPLC was performed with a linear gradient of acetonitrile(Merck) in water (5-40% or 65% acetonitrile over 40 min) on a 250-21Luna RP18 column (Phenomenex). To confirm peptide purity and identityanalytical HPLC and ESI-MS was employed.

Glu(NH—NH₂)-Ser-Pro-Thr-Ala-NH₂. (SEQ ID NO: 32). The linear precursorpeptide (Fmoc-Glu-Ser-Pro-Thr-Ala-NH₂) (SEQ ID NO: 33) was synthesizedaccording to standard Fmoc-procedures (Schilling, S. et al. 2002Biochemistry 41, 10849-10857) on Rink amide MBHA resin (Novabiochem).After cleavage of the Fmoc-protected peptide from the resin, the peptidewas precipitated with diethyl ether (Merck), filtered and dried. HMBA-AMresin (1.16 mmol/g, Novabiochem) was used for coupling of theγ-carboxylic acid group of glutamic acid of the precursor peptide (3eq.) in dichloromethane (DCM, Merck). Dicyclohexylcarbodiimide (DCC,Serva) (4 eq.) and dimethylaminopyridine (DMAP, Aldrich) (0.1 eq) wereused as coupling reagents. After 12 hours the resin was filtered, washedwith DCM and the reaction was repeated. After deprotection of theN-terminal Fmoc-group by employing 20% piperidine in DMF (3×5 min) thepeptide resin was treated with a 5% hydrazine solution (20 ml/g) for 1.5hours. The resin was filtered and washed with dimethylformamide (DMF,Roth, Germany) and TFA. Following evaporation, the crude peptide wasprecipitated with ether giving 76% yield.

H-Gln-Lys(Gln)-Arg-Leu-Ala-NH₂. The linear peptide was synthesizedaccording to standard Fmoc/^(t)Bu-procedure on Rink amide MBHA(Schilling, S. et al. 2002 Biochemistry 41, 10849-10857) usingFmoc-Lys(Fmoc)-OH as penultimate amino acid coupling. After deprotectionof the two amino protecting groups of lysine with 20% piperidine (Merck)in DMF, 4 eq. Fmoc-Gln(Trt)-OH were coupled. Standard cleavage procedureresulted in 95% yield.

H-Gln(NMe)-Phe-Lys-Ala-Glu-NH₂. (SEQ ID NO: 2).Fmoc-Gln(NMe)-OH wassynthesized starting from Fmoc-Glu-OtBu loaded on Fmoc-MI-AM(Novabiochem) resin. After swelling with DCM, the resin (0.5 g) waswashed with DMF and deprotected with 20% piperidine solution in DMF.Theresin was given into 5 ml DMF and 5 eq. Fmoc-Glu-OtBu, 5 eq. HATU and10 eq. DIPEA were added subsequently and shaked for 6 hours. Afterfiltration and washing, the product was cleaved according to standardTFA cleavage conditions. The peptide H-Gln(NMe)-Phe-Lys-Ala-Glu-NH₂ (SEQID NO: 2) was synthesized as described (Schilling, S. et al. 2002Biochemistry 41, 10849-10857). Fmoc-Gln(NMe)-OH was coupled withHATU/DIPEA overnight. Standard cleavage procedure resulted in 78% of thecrude peptide.

H-Glu(OMe)-β-naphthylamide, H-Gln-Val-OH, H-Gln-Tyr-OH. Boc-protecteddipeptides were synthesized applying standard mixed anhydride procedureby using isobutyl chlorocarbonate (Merck). The C-terminal methylestersBoc-Gln-Tyr-OMe and Boc-Gln-Val-OMe were saponified by 1N NaOH indioxane. The Boc-protected peptides were deprotected by HCl/dioxanesolution for 10 min. After evaporation the residue was crystallized withseveral solvents giving 60-70% of a solid compound.

H-Gln-cyclo(Nε-Lys-Arg-Pro-Ala-Gly-Phe). The linear precursorBoc-Gln(Trt)-Lys-Arg (Pmc)-Ala-Gly-Phe-OH (SEQ ID NO: 34) wassynthesized on acid sensitive 2-chlorotrityl resin. Coupling was carriedout using a standard protocol of Fmoc/^(t)Bu-strategy using Fmoc-Lys(Mtt)-OH. Aftercleavage with 3% TFA solution in DCM (10 times 5 min),the solution was neutralized with 10% pyridine (Merck) in methanol(MeOH; Merck), washed 3 times with DCM and MeOH, evaporated to 5% of thevolume and the crude peptide was precipitated with ice cold water.Following, the crude peptide was cyclized usingDCC/N-hydroxybenzotriazole (HOBt; Aldrich) activation. The crude peptidewas dissolved in dry dichloromethane (0.2 mmol/50 ml), 0.2 mmolN-methylmorpholine and 0.4 mmol 1-hydroxybenzotriazole were added. Thissolution was added dropwise to a solution of 0.4 mmoldicyclohexylcarbodiimide in 250 ml dichloromethaneat 0° C. The reactionwas completed by stirring overnight at room temperature. Afterfiltration of N,N′-dicyclohexylurea, the solvent was removed byevaporation. The residue was dissolved in ethyl acetate and washedseveral times with 1N HCl, saturated solution of NaHCO₃ and water. Thesolution was dried over anhydrous Na₂SO₄, filtered and evaporated todryness in vacuo.

Example 7 Characterization of Effectors of QC

Imidazole Derivatives

Imidazole and benzimidazole derivatives carrying substituents indifferent positions of the 5-membered ring were tested as inhibitors ofQC (Table 3). The constitution of the numbers refers to the imidazolering. The applied methods are described in example 2.

C-4(5) and C-4,5 Derivatives. The compounds carrying substitutions ineither in the constitutionally equivalent 4- or 5-position of theimidazole ring or in both positions showed a diminished potency forinhibition of human QC. The only exception, however, comprisedN-ω-acetylated histamine that proved to be one of the most potentinhibitory compounds. Small substituents in these positions had onlylittle effect on binding as indicated by the similar inhibition constantof 5-hydroxymethyl-4-methyl-imidazole compared to imidazole. Larger andmore bulky groups attached to these sites diminished or abolishedbinding of the compound by the enzyme. Some of the other substituentstested are known to exert negative inductive or mesomeric effects thatare capable to reduce the electron density in the imidazole ring, whichalso contributes to poorer binding constants. The difference in theK_(i)-values of L-histidine and histidinamide also indicate someinfluence of the charge on binding. Evidence for electrostatic repulsionof charged substrates were already shown in the substrate specificitystudies, i.e. glutaminamide was readily converted to products by humanQC, but no reactivity was observed for free glutamine as substrate.

C-2 Derivatives. All derivatives tested inhibited QC more weakly asimidazole. Any substitution bigger than a proton hinders properQC-binding. Only due to the methyl group in 2-methyl-benzimidazole, theinhibition constant drops about one order of magnitude. A very similarrelation was shown by comparison of the K_(i)-values for benzimidazoleand 2-amino-benzimidazole. Additionally, the results indicate that theinfluence is not related to electronic alterations.

N-1 Derivatives. Among the imidazole derivatives tested on inhibition ofhuman QC, most compounds that had improved K_(i)-values compared toimidazole showed alterations at one nitrogen atom. These compounds alsocontained one of the most effective QC inhibitors, 1-benzylimidazole.Interestingly, only little alterations of this structure led to a lossof inhibitory quality, as can be seen for 1-benzoylimidazole andphenylimidazole, which was inactive under the experimental conditions.Also in this case, the observed changes seemed not to be only caused bya reduced electron density of the imidazole ring due to the negativemesomeric effect of the Phenyl group, because also the bulkytrimethyl-silyl group, exhibiting a positive inductive effect showedreduced binding compared to other residues. Interestingly, one of theless effective compounds of this group was 1-aminopropyl-imidazole. Thesmall efficacy of this compound is caused by the basic amino group,since the sterically similar compounds 1-methylimidazole and1-vinylimidazole showed improved binding to the active site. Thus, thepositively charged amino group accounts for the smaller K_(i)-value, aresult that is corroborated by a comparison of the K_(i)-values ofN-ω-acetylated histamine (Table 3) and histamin (Table 4).

Effect of 3,4 and 3,5 Derivatization. The imidazole derivatives thatcontained substituents in positions 4(5) or both were shown to have arestricted efficiency for binding to the enzyme. The effect of thespecific substitutions were specified by comparison of the inhibitoryconstants of L-histamine and the two intermediates in the biologicaldegradation of histamine, 3-methyl-4-histamine and 3-methyl-5-histamine(Table 4). L-Histamine revealed a K_(i) value that was about one orderof magnitude smaller compared to its acetylated counterpart. Methylationof one nitrogen resulted in a considerable improvement of efficacy incase of 3-methyl-4-histamine. Methylation leading to3-methyl-5-histamine, however, resulted in a complete loss of inhibitoryactivity. Thus, the observed effect seems to be mainly caused by asterical hindrance of binding due to the derivatisation of the carbonadjacent to the basic nitrogen. Presumably, the basic nitrogen plays akey role for binding to the enzyme.

Example 8 Formation of Aβ3-40/42 Derivatives

The measurements were carried out with two short N-terminal peptidesequences of amyloid β-peptide 3-40(42/43), [Gln³]amyloid β-peptide1-11(sequence: DAQFRHDSGYE); SEQ ID NO: 35 and [Gln³]-amyloid β3-11, whichcontain a glutamine acid residue in the third position. Cleavage by DPIV and cyclization of the N-terminal glutamine residue by QC of the twopeptides was tested using MALDI-TOF mass spectrometry. Measurements werecarried out using purified DP IV (porcine kidney) or crude porcinepituitary homogenate as sources of QC as well as for both enzymes formeasurements of consecutive catalysis.

Results

1. Formation of [Gln³]Aβ3-11a from [Gln³]Aβ1-11a Catalysed by DPIV andits Prevent by the DP IV-Inhibitor Val-Pyrrolidide (Val-Pyrr)

DPIV or DPIV-like activity is cleaving [Gln³]Aβ1-11a under formation of[Gln³]Aβ3-11a (FIG. 7). The residue in the third position is uncoveredby this cleavage and becomes therefore accessible for modification byother enzymes, i.e. QC. As expected, catalysis can be completelyprevented by Val-Pyrr (FIG. 8).

2. Formation of [pGlu³]Aβ3-11a from [Gln³]Aβ3-11a by Catalysis of QC inPituitary Homogenate and Prevention by 1,10-phenanthroline

Glutaminyl cyclase present in the homogenate of porcine pituitarycatalyzes conversion of [Gln³]Aβ3-11a to [pGlu³]Aβ3-11a (FIG. 9).Formation of [pGlu³]Aβ3-11 a was inhibited by addition of1,10-phenanthroline (FIG. 10).

3. Consecutive Catalysis of DPIV and QC Resulting in Formation of[pGlu³]Aβ3-11a and Prevention by Val-Pyrr and 1,10-phenanthroline

Formation of [pGlu³]Aβ3-11a from [Gln³]Aβ1-11a takes place afterconsecutive catalysis by DP IV and QC, measured in crude homogenate ofporcine pituitary with added DPIV from porcine kidney (FIG. 11).[pGlu³]Aβ3-11a was not formed when the QC-inhibitor 1,10-phenanthroline(FIG. 12) or the DP IV-inhibitor Val-Pyrr was added (FIG. 13). Theslight appearance of [pGlu³]Aβ3-11a is due to aminopeptidase cleavageand following cyclization of the glutamine residue, also indicated byformation of [Gln³]Aβ2-11a.

4. Formation of [pGlu³]Aβ3-11a in Crude Pituitary Homogenate byCatalysis of Aminopeptidase(s)

Due to the formation of [pGlu³]Aβ3-11a that was not dependent on DPIVcatalysis, degradation of [Gln³]Aβ1-11a was investigated in crudepituitary homogenate without added DPIV (FIG. 14). As expected from thedata in section 4, formation of [pGlu³]Aβ3-11a was observed. The datashow that the degradation of [Gln³]Aβ1-11a may also be catalyzed byaminopeptidase(s), resulting in [pGlu³]Aβ3-11a. Hence, the results showthat pyroglutamyl formation is an endpoint of N-terminal peptidedegradation in this tissue, further supporting the role of QC in plaqueformation.

Example 9 Turnover of [Gln³]A□3-11a; 3-21a and 3-40 by Recombinant HumanQC

All [Gln³]Aβ derived peptides tested were efficiently converted by humanQC into the corresponding pyroglutamyl forms (Table 8). Due to the poorsolubility of [Gln³]Aβ3-21a and [Gln³]Aβ3-40 in aqueous solution, thedeterminations were carried out in presence of 1% DMSO. The bettersolubility of [Gln³]Aβ3-11a, however, allowed the kinetic analysis ofthe QC-catalyzed turnover in presence and absence of DMSO (Table 8).Taken together, the investigation of the Aβ peptides as QC-substrateswith chain-length of 8, 18 and 37 amino acids (see Table 8) confirmedthe observation that human QC-activity increases with the length of itssubstrates. Accordingly, Gln¹-gastrin, Gln¹-neurotensin, Gln¹-GnRH areamong the best QC-substrates taking the specificity constants intoaccount. Similarly, [Gln³]Aβ3-40 and glucagon, the largest QC-substratesinvestigated thus far, exhibited high second order rate constants (449mM⁻¹ s⁻¹ and 526 mM⁻¹ s⁻¹ respectively) even in presence of 1% DMSO(Table 8).

Interestingly, the kinetic parameters for the conversion of theinvestigated amyloid peptides did not change dramatically withincreasing size, suggesting only moderate effects of the C-terminal partof Aβ on QC catalysis. Therefore, due to better solubility andexperimental handling, the further investigations concerning N-terminalaminopeptidase processing of these peptides were performed using thesmaller fragments of Aβ, [Gln³]Aβ1-11a, [Gln³]Aβ3-11a and Aβ3-11a

TABLE 8 Kinetic parameters for conversion of N-terminally Gln-containingpeptides by recombinant human QC in buffer solution containing 1% DMSOPeptide K_(M) (μM) k_(cat) (s⁻¹) k_(cat)/K_(M) (mM⁻¹s⁻¹) [Gln³]Aβ3-11a 87 ± 3^(#)   55 ± 1^(#) 632 ± 10^(#) [Gln³]Aβ3-11a 155 ± 4 41.4 ± 0.4267 ± 4 [Gln³]Aβ3-21a 162 ± 12   62 ± 3 383 ± 10 [Gln³]Aβ3-40  89 ± 10  40 ± 2 449 ± 28 Glucagon(3-29)  19 ± 1 10.0 ± 0.2 526 ± 17^(#)Determined in absence of DMSO

Example 10 Turnover of Aβ3-11a and Aβ3-21a by Recombinant Human QC

The incubation of Aβ3-11a and Aβ3-21a in presence of QC revealed that incontrast to previous work, glutamate-containing peptides can also serveas QC-substrates (FIGS. 15C and D). The QC-catalyzed formation of[pGlu³]Aβ3-11a and [pGlu³]Aβ3-21a was investigated at pH 5.2 and 6.5,respectively. If the QC-inhibitor benzimidazole was added to thesolution before starting the assay by addition of QC, substrateconversion resulting in [pGlu³]Aβ3-11a or [pGlu³]Aβ3-21a was suppressed(FIGS. 15E and F). If QC was boiled before addition, formation of thepGlu-peptides was negligible (FIGS. 15A and B).

Example 11 pH-Dependency of the Papaya QC-Catalyzed Cyclization ofGln-βNA and Glu-βNA

Papaya QC converted Glu-βNA in a concentration range up to 2 mM (whichwas limited by substrate solubility) in accordance with Michaelis-Mentenkinetics (FIG. 16). Inspection of turnover versus substrateconcentration diagrams for the QC-catalyzed conversion of Glu-βNA,studied between pH 6.1 and 8.5, revealed that for this Glu-substrateboth parameters, K_(M) and k_(cat), changed in a pH-dependent manner(FIG. 16). This is in contrast to the previously described QC-catalyzedglutamine cyclization, for which only changes in K_(M) were observedover the given pH range (Gololobov, M. Y., Song, I., Wang, W., andBateman, R. C. (1994) Arch Biochem Biophys 309, 300-307).

Subsequently, to study the impact of the proton concentration duringGlu- and Gln-cyclization, the pH-dependence of cyclization of Glu-βNAand Gln-βNA under first-order rate-law conditions (i.e. substrateconcentrations far below K_(M)-values) was investigated (FIG. 17). Thecyclization of glutamine has a pH-optimum at pH 8.0, in contrast to thecyclization of glutamic acid which showed a pH-optimum of pH 6.0. Whilethe specificity constants at the respective pH-optima differapproximately 80,000-fold, the ratio of QC versus EC activity around pH6.0, is only about 8,000.

The nonenzymatic pGlu-formation from Gln-βNA investigated at pH 6.0, wasfollowed for 4 weeks and revealed a first-order rate constant of1.2*10⁻⁷ s⁻¹. However, during the same time period, no pGlu-βNA wasformed from Glu-βNA, allowing to estimate a limiting rate constant forturnover of 1.0*10⁻⁹ s⁻¹.

Example 12 Enzyme Inactivation/Reactivation Procedures

An aliquot of human QC (0.1-0.5 mg, 1 mg/ml) was inactivated overnightby dialysis against a 3000-fold excess of 5 mM 1,10-phenanthroline or 5mM dipicolinic acid in 0.05 M Bis-Tris/HCl, pH 6.8. Subsequently, theinactivating agent was carefully removed by dialysis (3 cycles,2000-fold excess) of the samples against 0.05 M Bis-Tris/HCl, pH 6.8,containing 1 mM EDTA. Reactivation experiments were performed at roomtemperature for 15 minutes using Zn⁺⁺, Mn⁺⁺, Ni⁺⁺, Ca⁺⁺, K⁺ and Co⁺⁺ions at concentrations of 1.0, 0.5, 0.25 mM in 0.025 M Bis-Tris,pH 6.8containing 0.5 mM EDTA. QC activity assays were performed in 0.05 MTris/HCl, pH 8.0, containing 2 mM EDTA, in order to avoid a rapidreactivation by traces of metal ions present in buffer solutions.

The inhibition of porcine QC by 1,10-phenanthroline has already beendescribed (Busby, W. H. J. et al. 1987 J Biol Chem 262, 8532-8536,Bateman, R. C. J. et al. 2001 Biochemistry 40). However, the fact thatEDTA has been shown to have an activating effect on QC catalysissuggested that inhibition by phenanthroline is not due to metalchelation (Busby, W. H. J. et al. 1987 J Biol Chem 262, 8532-8536,Bateman, R. C. J. et al. 2001 Biochemistry 40). Also, in addition tobeing inhibited by 1,10-phenanthroline, human QC catalyzed substratecyclization was abolished in presence of dipicolinic acid and8-hydroxyquinoline, other inhibitors of metalloenzymes. These chelatorsinhibited QC in a competitive and time-dependent manner, i.e., alreadycompetitively inhibited initial activity was found to be further reducedafter prolonged incubation with the compounds (FIGS. 18, 19).Interestingly, EDTA did not show remarkable inhibition regardless ofincubation time or under any conditions.

Human QC was almost completely inactivated after extensive dialysisagainst 5 mM 1,10-phenanthroline or 5 mM dipicolinic acid. Afterrepeated dialysis overnight against chelator-free buffer solutions, QCactivity was partially reactivated up to 50-60%. However, when dialyzedagainst buffers containing 1 mM EDTA, no reactivation was observed.

Near-total restoration of QC activity after inactivation by eitherdipicolinic acid or 1,10-phenanthroline was achieved by incubating theprotein for 10 minutes with 0.5 mM ZnSO₄ in presence of 0.5 mM EDTA(FIG. 20). Partial restoration of QC activity was similarly obtainedusing Co⁺⁺ and Mn⁺⁺ ions for reactivation. Even in the presence of 0.25mM Zn⁺⁺ a reactivation up to 25% of the original activity was possible.No reactivation was observed applying Ni⁺⁺, Ca⁺⁺ or K⁺ ions. Similarly,incubation of fully active QC with these ions had no effect on theenzyme activity.

1. A method of treating Alzheimer's disease, comprising administering toa mammalian subject in need thereof a composition comprising aninhibitor of glutaminyl cyclase, or a pharmaceutically acceptable saltthereof.
 2. The method according to claim 1, wherein said inhibitor ofglutaminyl cyclase is administered in a pharmaceutical composition forparenteral, enteral or oral administration, which further comprises atleast one pharmaceutically acceptable carrier or excipient.
 3. Themethod according to claim 2, wherein said pharmaceutical compositionadditionally comprises at least one agent selected from the groupconsisting of: i) inhibitors of DP IV or DP IV-like enzymes, ii)aminopeptidase-inhibitors, and iii) substrates, pseudosubstrates,inhibitors of glutaminyl cyclase expression, binding proteins orantibodies of enzyme proteins that reduce the glutaminyl cyclase proteinconcentration.
 4. The method according to claim 3, wherein the DPIV-inhibitor is selected from the group consisting of L-threo-isoleucylthiazolidine, L-allo-isoleucyl thiazolidine, L-threo-isoleucylpyrrolidine, L-allo-isoleucyl pyrrolidine,NVP-DPP728A(1-[[[2-[{5-cyanopyridin-2-yl}amino]ethyl]amino]acetyl]-2-cyano-(S)-pyrrolidine),LAF-237(1-[(3-hydroxy-adamant-1-ylamino)-acetyl]-pyrrolidine-2(S)-carbonitrile);TSL-225 (tryptophyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid),FE-999011, N-valyl prolyl, O-benzoyl hydroxylamine, alanyl pyrrolidine,H-Asn-pyrrolidine, H-Asn-thiazolidine, H-Asp-pyrrolidine,H-Asp-thiazolidine, H-Asp(NHOH)-pyrrolidine, H-Asp(NHOH)-thiazolidine,H-Glu-pyrrolidine, H-Glu-thiazolidine, H-Glu(NHOH)-pyrrolidine,H-Glu(NHOH)-thiazolidine, H-His-pyrrolidine, H-His-thiazolidine,H-Pro-pyrrolidine, H-Pro-thiazolidine, H-Ile-azididine,H-Ile-pyrrolidine, H-L-allo-Ile-thiazolidine, H-Val-pyrrolidine andH-Val-thiazolidine, 2-Amino octanoic acid-Pro-Ile, Abu-Pro-Ile,Aib-Pro-Ile, Aze-Pro-Ile, Cha-Pro-Ile, Ile-Hyp-Ile, Ile-Pro-allo-Ile,Ile-Pro-t-butyl-Gly, Ile-Pro-Val, Nle-Pro-Ile, Nva-Pro-Ile, Orn-Pro-Ile,Phe-Pro-Ile, Phg-Pro-Ile, Pip-Pro-Ile, Ser(Bzl)-Pro-Ile, Ser(P)-Pro-Ile,Ser-Pro-Ile, t-butyl-Gly-Pro-D-Val, t-butyl-Gly-Pro-Gly,t-butyl-Gly-Pro-Ile, t-butyl-Gly-Pro-Ile-amide,t-butyl-Gly-Pro-t-butyl-Gly, t-butyl-Gly-Pro-Val, Thr-Pro-Ile,Tic-Pro-Ile, Trp-Pro-Ile, Tyr(P)-Pro-Ile, Tyr-Pro-allo-Ile,Val-Pro-allo-Ile, Val-Pro-t-butyl-Gly, Val-Pro-Val, and pharmaceuticallyacceptable salts thereof.
 5. The method according to claim 3, whereinthe DP IV-inhibitor is selected from the group consisting of2-Methylcarbonyl-1-N-[(L)-Alanyl-(L)-Valinyl]-(2S)-pyrrolidinehydrobromide,2-Methyl)carbonyl-1-N-[(L)-Valinyl-(L)-Prolyl-(L)-Valinyl]-(2S)-pyrrolidinehydrobromide,2-[(Acetyl-oxy-methyl)carbonyl]-1-N-[(L)-Alanyl-(L)-Valinyl]-(2S)-pyrrolidinehydrobromide,2-[Benzoyl-oxy-methyl)carbonyl]-1-N-[{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidinehydrobromide,2-{[(2,6-Dichlorbenzyl)thiomethyl]carbonyl}-1-N-[{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidine,2-[Benzoy-loxy-methyl)carbonyl]-1-N-[Glycyl-(L)-Valinyl]-(2S)-pyrrolidinehydrobromide,2-[([1,3]-Thiazolethiazol-2-yl)carbonyl]-1-N-[{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidinetrifluoracetate,2-[(Benzothiazolethiazol-2-yl)carbonyl]-1-N-[N-{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidinetrifluoracetate,2-[(-Benzothiazolethiazol-2-yl)carbonyl]-1-N-[{(L)-Alanyl}-Glycyl]-(2S)-pyrrolidinetrifluoracetate,2-[(Pyridin-2-yl)carbonyl]-1-N-[N-{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidinetrifluoracetate, 1-cyclopentyl-3-methyl-1-oxo-2-pentanaminium chloride,1-cyclopentyl-3-methyl-1-oxo-2-butanaminium chloride,1-cyclopentyl-3,3-dimethyl-1-oxo-2-butanaminium chloride,1-cyclohexyl-3,3-dimethyl-1-oxo-2-butanaminium chloride,3-(cyclopentylcarbonyl)-1,2,3,4-tetrahydroisoquinolinium chloride, andN-(2-cyclopentyl-2-oxoethyl)cyclohexanaminium chloride, and otherpharmaceutically acceptable salts thereof.
 6. The method according toclaim 3, wherein the H-isoAsp-Ala-OH generating activity of the DPIV-like enzyme is blocked.
 7. The method according to claim 6, whereinthe DP IV-like enzyme is DP II.
 8. The method according to claim 1,wherein the glutaminyl cyclase inhibitor is a competitive inhibitor. 9.The method according to claim 1, wherein the glutaminyl cyclaseinhibitor has a K_(i)-value of about 0.0071 mM or below.
 10. The methodaccording to claim 1, wherein the glutaminyl cyclase inhibitor has aK_(i)-value in the range of from about 0.00041 mM to about 0.0071 mM.11. The method according to claim 10, wherein the glutaminyl cyclaseinhibitor is selected from the group consisting of:3-(1H-imidazol-1-yl)-1-(3-methylbenzo[b]thiophene-2-yl)propan-1-one

4-[(1-methyl-1H-imidazol-5-yl)methyl]-3-propyldihydrofuran-2-(3H)-one

4-[2-(1H-imidazol-1-yl)-ethoxy]benzoic acid

3-[3-(1H-imidazol-1-yl)propyl]-2-thioxoimidazolidin-4-one

5-nitro-2-[2-([{3-(1H-imidazol-1-yl-)propyl}amino]carbonyl)phenyl]furamide

1-benzylimidazole.


12. The method according to claim 1, wherein said inhibitor ofglutaminyl cyclase inhibits the conversion of N-terminal glutamic acidor glutamine residues to pyroglutamic acid residues of at least onesubstrate of glutaminyl cyclase selected from the group consisting ofAβ3-40/42, [Gln³]Aβ3-40/42, [Glu¹¹]Aβ11-40/42, [Gln¹¹]Aβ11-40/42,[Gln¹]Gastrins (17 and 34), [Gln¹]Neurotensin,[Gln¹]FPP, [Gln¹]TRH,[Gln¹]GnRH, [Gln¹]CCL 2, [Gln¹]CCL 7, [Gln¹]CCL 8, [Gln¹]CCL 16,[Gln¹]CCL 18, [Gln¹]ELA, [Gln¹]Fractalkine, and [Gln¹]Orexin A.
 13. Themethod according to claim 1, wherein the administration of saidinhibitor of glutaminyl cyclase inhibits the conversion of N-terminalglutamic acid or glutamine residues to pyroglutamic acid residues of atleast one substrate of glutaminyl cyclase selected from the groupconsisting of Aβ3-40/42, [Gln³]Aβ3-40/42, [Glu¹¹]Aβ11-40/42 and[Gln¹¹]Aβ11-40/42.
 14. The method according to claim 1, wherein saidinhibitor of glutaminyl cyclase binds to the active-site bound metal ionof glutaminyl cyclase.
 15. A method of inhibiting the conversion ofN-terminal glutamic acid or glutamine residues to pyroglutamic acidresidues of at least one substrate of glutaminyl cyclase in a mammaliansubject comprising: administering to a mammalian subject in need thereofa composition comprising an inhibitor of glutaminyl cyclase, or apharmaceutically acceptable salt thereof; wherein the inhibitor ofglutaminyl cyclase inhibits the conversion of N-terminal glutamic acidor glutamine residues to pyroglutamic acid residues of at least onesubstrate of glutaminyl cyclase selected from the group consisting ofAβ3-40/42, [Gln³]Aβ3-40/42, [Glu¹¹]Aβ11-40/42, [Gln ¹¹]Aβ11-40/42,[Gln¹]Gastrins (17 and 34), [Gln¹]Neurotensin, [Gln¹]FPP, [Gln¹]TRH,[Gln¹]GnRH, [Gln¹]CCL 2, [Gln¹]CCL 7, [Gln¹]CCL 8, [Gln¹]CCL 16,[Gln¹]CCL 18, [Gln¹]ELA, [Gln¹]Fractalkine, and [Gln¹]Orexin A in themammalian subject; and the mammalian subject is diagnosed withAlzheimer's disease.
 16. The method according to claim 15, wherein theadministration of said inhibitor of glutaminyl cyclase inhibits theconversion of N-terminal glutamic acid or glutamine residues topyroglutamic acid residues of at least one substrate of glutaminylcyclase selected from the group consisting of Aβ3-40/42,[Gln³]Aβ3-40/42, [Glu¹¹]Aβ11-40/42 and [Gln¹¹]Aβ1140/42.
 17. The methodaccording to claim 15, wherein said inhibitor of glutaminyl cyclase isadministered in a pharmaceutical composition for parenteral, enteral ororal administration, which further comprises at least onepharmaceutically acceptable carrier or excipient.
 18. The methodaccording to claim 17, wherein said pharmaceutical compositionadditionally comprises at least one agent selected from the groupconsisting of: i) inhibitors of DP IV or DP IV-like enzymes, ii)aminopeptidase-inhibitors, and iii) substrates, pseudosubstrates,inhibitors of glutaminyl cyclase expression, binding proteins orantibodies of enzyme proteins that reduce glutaminyl cyclase proteinconcentration.
 19. The method according to claim 18, wherein the DPIV-inhibitor is selected from the group consisting of L-threo-isoleucylthiazolidine, L-allo-isoleucyl thiazolidine, L-threo-isoleucylpyrrolidine, L-allo-isoleucyl pyrrolidine, NVP-DPP728A(1-[[[2-[{5-cyanopyridin-2-yl}amino]ethyl]amino]acetyl]-2-cyano-(S)-pyrolidine), LAF-237(1-[(3-hydroxy-adamant-1-ylamino)-acetyl]-pyrolidine-2(S)-carbonitrile);TSL-225 (tryptophyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid),FE-999011, N-valyl prolyl, O-benzoyl hydroxylamine, alanyl pyrrolidine,H-Asn-pyrrolidine, H-Asn-thiazolidine, H-Asp-pyrrolidine,H-Asp-thiazolidine, H-Asp(NHOH)-pyrrolidine, H-Asp(NHOH)-thiazolidine,H-Glu-pyrrolidine, H-Glu-thiazolidine, H-Glu(NHOH)-pyrolidine,H-Glu(NHOH)-thiazolidine, H-His-pyrrolidine, H-His-thiazolidine,H-Pro-pyrrolidine, H-Pro-thiazolidine, H-Ile-azididine,H-Ile-pyrolidine, H-L-allo-Ile-thiazolidine, H-Val-pyrrolidine andH-Val-thiazolidine, 2-Amino octanoic acid-Pro-Ile, Abu-Pro-Ile,Aib-Pro-Ile, Aze-Pro-Ile, Cha-Pro-Ile, Ile-Hyp-Ile, Ile-Pro-allo-Ile,Ile-Pro-t-butyl-Gly, Ile-Pro-Val, Nle-Pro-Ile, Nva-Pro-Ile, Orn-Pro-Ile,Phe-Pro-Ile, Phg-Pro-Ile, Pip-Pro-Ile, Ser(Bzl)-Pro-Ile, Ser(P)-Pro-Ile,Ser-Pro-Ile, t-butyl-Gly-Pro-D-Val, t-butyl-Gly-Pro-Gly,t-butyl-Gly-Pro-Ile, t-butyl-Gly-Pro-Ile-amide,t-butyl-Gly-Pro-t-butyl-Gly, t-butyl-Gly-Pro-Val, Thr-Pro-Ile,Tic-Pro-Ile, Trp-Pro-Ile, Tyr(P)-Pro-Ile, Tyr-Pro-allo-Ile,Val-Pro-allo-Ile, Val-Pro-t-butyl-Gly, Val-Pro-Val, and pharmaceuticallyacceptable salts thereof.
 20. The method according to claim 18, whereinthe DP IV-inhibitor is selected from the group consisting of2-Methylcarbonyl-1-N-[(L)-Alanyl-(L)-Valinyl]-(2S)-pyrrolidinehydrobromide,2-Methyl)carbonyl-1-N-[(L)-Valinyl-(L)-Prolyl-(L)-Valinyl]-(2S)-pyrrolidinehydrobromide,2-[(Acetyl-oxy-methyl)carbonyl]-1-N-[(L)-Alanyl-(L)-Valinyl]-(2S)-pyrrolidinehydrobromide,2-[Benzoyl-oxy-methyl)carbonyl]-1-N-[{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidinehydrobromide,2-{[(2,6-Dichlorbenzyl)thiomethyl]carbonyl}-1-N-[{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidine,2-[Benzoy-Ioxy-methyl)carbonyl]-1-N-[Glycyl-(L)-Valinyl]-(2S)-pyrrolidinehydrobromide,2-[([1,3]-Thiazolethiazol-2-yl)carbonyl]-1-N-[{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidinetrifluoracetate,2-[(Benzothiazolethiazol-2-yl)carbonyl]-1-N-[N-{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidinetrifluorace2-[(-Benzothiazolethiazol-2-yl)carbonyl]-1-N-[{(L)-Alanyl}-Glycyl]-(2S)-pyrrolidinetrifluoracetate,2-[(Pyridin-2-yl)carbonyl]-1-N-[N-{(L)-Alanyl}-(L)-Valinyl]-(2S)-pyrrolidinetrifluoracetate, 1-cyclopentyl-3-methyl-1-oxo-2-pentanaminium chloride,1-cyclopentyl-3-methyl-1-oxo-2-butanaminium chloride,1-cyclopentyl-3,3-dimethyl-1-oxo-2-butanaminium chloride,1-cyclohexyl-3,3-dimethyl-1-oxo-2-butanaminium chloride,3-(cyclopentylcarbonyl)-1,2,3,4-tetrahydroisoquinolinium chloride, andN-(2-cyclopentyl-2-oxoethyl)cyclohexanaminium chloride, and otherpharmaceutically acceptable salts thereof.
 21. The method according toclaim 18, wherein the H-isoAsp-Ala-OH generating activity of the DPIV-like enzyme is blocked.
 22. The method according to claim 21, whereinthe DP IV-like enzyme is DP II.
 23. The method according to claim 15,wherein the glutaminyl cyclase inhibitor is a competitive inhibitor. 24.The method according to claim 15, wherein the glutaminyl cyclaseinhibitor has a K_(i)-value of about 0.0071 mM or below.
 25. The methodaccording to claim 24, wherein the glutaminyl cyclase inhibitor has aK_(i)-value in the range of from about 0.00041 mM to about 0.0071 mM.26. The method according to claim 15, wherein the glutaminyl cyclaseinhibitor is selected from the group consisting of:3-(1H-imidazol-1-yl)-1-(3-methylbenzo[b]thiophene-2-yl)propan-1-one

4-[(1-methyl-1H-imidazol-5-yl)methyl]-3-propyldihydrofuran-2-(3H)-one

4-[2-(1H-imidazol-1-yl)-ethoxy]benzoic acid

3-[3-(1H-imidazol-1-yl)propyl]-2-thioxoimidazolidin-4-one

5-nitro-2-[2-([{3-(1H-imidazol-1-yl-)propyl}amino]carbonyl)phenyl]furamide

1-benzylimidazole.


27. The method according to claim 15, wherein said inhibitor ofglutaminyl cyclase binds to the active-site bound metal ion ofglutaminyl cyclase.